The original meaning of the American-English expression cookie pusher was: a fashionable young man who enjoys socialising with women at tea parties or other social events.—Synonym: cake eater.

The earliest occurrences of cookie pusher that I have found indicate that this expression originated in 1922, in connexion with the flappers ¹, in the slang of high-school and university students in Kansas City ², Missouri, and in the state of Kansas.

¹ The flappers were the young women who, in the 1920s, were intent on enjoying themselves and flouted conventional standards of behaviour.—Cf. “the cat’s whiskers”, and all that jazz.
² Kansas City metropolitan area straddles the Kansas-Missouri state line.

These early occurrences are as follows, in chronological order:

1-: From The Kansas City Star (Kansas City, Missouri) of Tuesday 7^th February 1922:

NEW WESTPORT BOYS’ CLUBS.
The “Cookie Pushers,” “Candy Kids” and “Tea Hounds” Form.

The “cake eaters” have hogged the center of the stage long enough. Now they must share honors with kindred species of boy flappers, the “cookie pushers,” “candy kids” and “tea hounds.”
Last night the four species were given recognition by the boys’ club of Westport high school ³. A membership and attendance contest was started, the members being divided into four groups. At the end of six weeks a dinner is to be given by the two groups showing the lowest percentage of attendance at the weekly club meetings.
One object of the groups is to belie their names. The “cake eaters” say they are not going to wear the super-belled [?] corduroy trousers adopted by some of their classmates. Indeed, their leader wears the uniform of a lieutenant of the R. O. T. C. ⁴, on which trousers with flapping bottoms are decidedly not regulation.
Leaders of the groups: “Cake eaters,” George Peake, 3913 Broadway; “cookie pushers,” Ray Voskamp, 5021 Tracy; “candy kids,” Ed Weatherly, 7421 Main; “tea hounds,” Leonard Kniffin, 4029 Warwick.
The boys’ club is organized under the Y. M. C. A. and has about one hundred members. The meeting last night was at the Calvary Baptist church.

³ Westport High School was located in Kansas City, Missouri.
⁴ R. O. T. C. is the abbreviation of Reserve Officers’ Training Corps, which denotes a college- and university-based program preparing young adults to become officers in the U.S. Armed Forces.

2-: From the Sunflowers column, published in The Kansas Industrialist (Manhattan, Kansas) ⁵ of Wednesday 29^th March 1922:

COLLEGE TALK

Going to college and going back to college are entirely different. The college changes, new buildings spring up, new students take the places of the old, but greatest and fastest of all is the change in college language. The English of today is not what she was night before last.
For the benefit of the old boys and girls who used to caper around over the campus and knock the king’s English for a goal now and then, we are appending the following dictionary of college life as it is spoken in the spring of 1922. Alumni journeying back to spring festival and commencement will find it an invaluable aid if the language has not entirely changed color by the time they get here.
BERRIES. N. neuter. A word used in questions to indicate surprise and approval. “Isn’t that the Berries!” means “Ain’t that just grand!”
TOMATO. Adj. Very nice. “That’s very tomato” means that everything is hunkydory.
TIN CAN. Adj. Truly delightful. Anything that speeds up the blood a bit is tin can.
GOLD DIGGER. N. fem. A girl that spends a cake eater’s money relentlessly. One who will not compromise on cokes or root beer but insists on eating the whole menu. A pocket twister.
SLICK. Adj. Came into use shortly after boys began using bear grease and brilliantine on their hair. A slick date is a young man who is polished and gives the impression of having got by with a whole lot. He is extra successful in college love affairs, is invariably suspected of having sowed more than his share of wild oats, is good looking, cynical, and knows his stuff.
KNOCKOUT. N. fem. A flapper who knocks them back up against the wall. A classy knockout is a young lady who is so attractive as to make all the cake eaters drop their cake on the floor.
DOGS. N. masc. and fem. Oversize feet. Dogs above number nines are referred to as Airedales.
SAD. Adj. Refers to a poor but honest girl who powders moderately but doesn’t paint or lipstick any. She makes a favorable impression on people who are looking for somebody with sense, but nobody else ever notices her.
SERAPH. N. fem. A young lady who likes to be kissed with lots of repression as in the good old colonial days.
WRESTLE. N. common. A dance engaged in by a flapper and a cookie pusher.
H. W. D.

⁵ The Kansas Industrialist was the student newspaper of the Kansas State Agricultural College, Manhattan, Kansas.

3-: From Our Column, by Guy Harris, published in The White City Register (White City, Kansas) of Thursday 6^th April 1922:

Upon reading the cleverly written “Sunflowers” column in the Kansas Industrialist we ran across the term “cookie pusher” as relating as near as we can determine, to a member of the masculine sex of college student. Just recently we have found out what “cake eater” typifies. Now what the deuce is the difference between a cake eater and a cookie pusher?

4-: From The University Daily Kansan (Lawrence, Kansas) ⁶ of Thursday 6^th April 1922:

Plain Tales from the Hill

A fourth ticket appeared on the Hill this morning which not only caused a great fluttering among the newly named candidates, but also a grave foreboding in the hearts of those who considered themselves the only ones on the first three tickets. This apprehension was finally culminated by the issue of a challengy [sic] by the D. & C. ticket which, with the complete list of Cookie Munchers, is herewith printed:
CAKE EATERS TICKET
Council Officers – Qualifications
Pres., Carl McAdams – Rubs down with tea
Vice-Pres., Jerry Penny – Never cracked a tea cup
Second Vice-Pres., Dutch Jaedicke – All-star tea sipper
Sec., Chuck Fratcher – Pushes his cookie well
Treas., Jimmy Dye – Never dropped a crumb
Cheer Leader, Eddie Engel – Petting Artist
College Representatives
Wendall Smith – Wiedeman’s Idol
George Hollingberry – Long Distance Tea Drinker
Carl Duffie – Cookie Pusher
Don Ellis – Never eats with his knife
Francis Prosser – Applicant for Tea Hound League
[…]
Challenge
We the Dollars and Cents ticket hereby challenge the Cake Eaters Party to a cookie rolling contest up 14^th Street.
Signed,
Dollars and Cents.

⁶ The University Daily Kansan was the student newspaper of the University of Kansas:

5-: From The Minneapolis Better Way (Minneapolis, Kansas) of Thursday 20^th April 1922:

Cake eaters and cookie pushers are still giving this community the go by. However, one night last week we did see a wonderful specimen in his wild state of an oiled and very much be-slicked lounge lizard roaming aimlessly about the high school building. We would very mucr [sic] like to have captured this splendid specimen alive and hand it down to posterity, but a couple of flappers came along and took it away with them before we could put out our bait of jelly rolls.

4-: From The University Daily Kansan (Lawrence, Kansas) of Wednesday 26^th April 1922:

The Fable of the Cookie Pusher

Rollo was a Creature of an Unusual Sort. Ever since his days in the Grade School he had had Wavy Hair and a Way with the Women which made all the Other Fellows take to the Brush. He wasn’t much of a Student and the hardest Work he had ever done by the Time he had Arrived at the College Age was cranking a Victrola. But he was There.
The first day he Landed on the Hill the Boys all got Together and decided he was Fraternity Material even if they had to Crack some of the Pan-Hellenic By-laws to get him Spiked. They invited him to a Gallop or Two and took Note of the Fact that when he got out on the Polished Hardwood it was quite Apparent that he was Familiar with his Hen Fruit. So the Winners brought him down to the House and put a Pin in his Lapel.
By his Sophomore Year, Rollo was easily the Lion of the Crowd. Nobody thought of staging a Soup-and-Fish without asking Him to Honor Them and when he turned loose his Line on the Frails they could Hear the strains of Mendelsohn in the distance. The Phi Beta Kappas missed him in the Rush but he went out for Tennis in the Mixed Doubles and played a Shrewd Hand of Bridge so everything was Lovely. During his Last and he used to give the Angry Mob a Treat by driving down the Main Drag with something in Beside Him that was a Cross between Agnes Ayres and the Dutchess of Marlborough. When he went out into the Cruel Woild his Dizzy Friends predicted the Best in the way of Success for Him.
For the past Several Moons he has Held Down the Position of Assistant Cashier in the Home City Bank at 80 Beans a mo. but he writes the Boys that as soon as the Ante is Lifted to an Even Hundred he will make an Extended Visit.
(MORAL—He should have Passed Away as a Child.)

5-: From The Wichita Daily Eagle (Wichita, Kansas) of Friday 28^th April 1922:

Get New Names.—Cake Eaters have gone into the discard in Wichita, insofar as their names are concerned, according to young women who are considered authority on such subject. They no longer are dubbed “cake eaters,” but are called “cookie pushers” and “gutter pups.”

The expression cookie pusher came to denote a diplomat employed by the U.S. State Department, regarded as being excessively occupied with entertaining dignitaries and doing little meaningful work. The earliest occurrence that I have found is from The Evening Star (Washington, D.C.) of Thursday 17^th January 1924:

Spats, Tea, Cookie Types of Envoys Hit at Hearing

“White spats, tea drinkers and cookie pushers” should be eliminated from the diplomatic corps, Hugh Gibson, minister to Poland, told the House foreign affairs committee in urging passage of the Rogers bill for reorganization of the diplomatic and consular services.
Mr. Gibson declared that “halo chasers” also are unwholesome elements in the services and under the bill could be relegated to inconspicuous places.
Wilbur J. Carr, director of the consular service, told the committee the increased salaries provided by the measure would both attract and retain valuable men.