The colloquial American-English expression rocking-chair money denotes unemployment insurance, and, broadly, any benefit paid to someone who is not working.
—Cf. also the expressions rocking-chair job and sit-down money.

The expression rocking-chair money was first defined in the following from The Bee (Danville, Virginia) of Thursday 30^th June 1938:

STEP UP IN MILL TIME IMMINENT
Suddenly Stimulated Market Brings Hope of Longer Work Week in July

Although officials of the Riverside and Dan River Cotton Mills declined today to be quoted or to engage in any speculative theories, there is a well pronounced belief, which has authentic backing that the working hours in the Danville plants will be stepped up materially during the early part of July.
[…]
Increased working opportunities are said to be desired by the textile workers who are tired of excessive leisure time and who are anxious to avail of a broader personal budget. An increase in the working hours will result in some further adjustment of unemployment insurance which has come to be known among the mill workers as “rocking chair” money but will add to the weekly payroll in such a way as to be reflected in a measure of mercantile recovery.

The earliest occurrence of the expression rocking-chair money that I have found is from the following advertisement, published in the preceding issue, i.e. that of Wednesday 29^th June 1938, of the same newspaper, i.e. The Bee (Danville, Virginia)—this advertisement perhaps puns on rocking-chair money as an appellation for unemployment insurance:

Furniture, Household Goods 65
Big Assortment Rockers
Spend ‘rocking-chair’ money here.
Clutter Furniture Co.
128 N. Union St.

The expression rocking-chair money then occurs in the following from The Times-News (Hendersonville, North Carolina) of Thursday 14^th July 1938—reprinted from the Gastonia Daily Gazette (Gastonia, North Carolina):

THEY DON’T HAVE TO STAY ON WPA *

Striking WPA workers in Charlotte Wednesday were given to understand, in no uncertain terms, that they must “give an honest day’s work for an honest day’s pay.”
This is worthy of note because, up to now, in this part of the country at least, the WPA worker who had any notion that he was expected to render to Uncle Sam the same kind of service that he would render to private business or industry was the rare exception.
The lazy, indolent manner in which WPA workers as a rule performed theri [sic] duties brought the relief system and the government itself into disrepute. Jokes about WPA workers have been the street corner conversation foundation for a long time. Even those who are living on Uncle Sam’s bounty are heard to refer to their payments as “rocking-chair money.” It has been a national scandal.

* The Works Progress Administration (WPA) was a work program for the unemployed, created in 1935 by Franklin Delano Roosevelt (1882-1945), President of the USA from 1933 to 1945, as part of the New Deal, i.e. the economic measures introduced in 1933 to counteract the effects of the Great Depression.

Another early occurrence of the expression rocking-chair money is from the column This World Of Ours, published in The Greenville News (Greenville, South Carolina) of Tuesday 11^th October 1938:

“Rocking Chair” Money

The latest thing we have heard in twisting the English language to fit is “rocking-chair” money. This apt expression is applied to the checks being received from the state unemployment commission, which represents pay for half the time lost when laid off from jobs due to no fault of the employe. The money seemed so “easy” that some one dubbed it “rocking-chair” money, and the expression has become an accepted definition.—Belton News.

The following seems to indicate that the expression rocking-chair money was coined on various occasions by different persons, independently from each other—it is from the column Koon Holler Reporter, published in The Journal (Caldwell, Ohio) of Thursday 4^th March 1954:

ROCKING CHAIR MONEY

Dear Editor:
I have noticed that each generation coins a lot of new words. Just found out the young people who get paid for not working have coined a now common expression, “rockingchair money”. This is a new one on me.
Gosh, it is marvelous to sit in a rocking chair and have a check come in every week. I have known about an expression, “Security from birth to death.” But to sit and rock away the years that is sure going some.
I really feel it would be still a little better to have the government send an expert into such homes and prepare the meals and have a trained nurse feed the poor helpless people.
There are people who have a pecular idea about life. If you do them a little favor like fixing up their fence they expect you to keep right on doing it for them. If you gather their eggs just once then you have a permanent job. When the government got into this fence fixing they can just keep right on fixing it. If a man has red blood in his veins he wants none of this stupidity.
It has been suggested that people who work and pay taxes to keep a certain class in a rocking chair should raise bees. Guess that would be OK for they are stung by every organization known by man. You may get thru life in these United States but one thing is sure you can’t go to heaven in a rocking chair.
Yours for less idleness.
Uncle Sam Stille.