The Irish- and British-English noun knocker-up was used to designate a person who goes round the streets in the early morning to awaken factory hands—who were fined, or even sacked, if they arrived at the factory after work had commenced.

And knocking-up was used—as a noun and attributively—of the business consisting in going round the streets in the early morning to awaken factory workers.

The following description is from Occasional Notes, published in The Pall Mall Gazette (London, England) of Tuesday 14^th October 1884 [Vol. 40, No. 6,114, page 3, column 2]:

The stock in trade of the “knocker-up” consists of a long pole, something like a lamplighter’s rod, with pieces of wire at the end. This pole is raised to the bedroom, and the wires are rattled against the window pane. Knockers-up charge 2d. a week for this service, and those with the largest practice have as many as one hundred houses on their lists. They are most of them old men, but there are a few old women also in the trade.

And the following photograph and caption are from the Express and Star and Birmingham Evening Express (Wolverhampton, Staffordshire, England) of Monday 26^th February 1962 [No. 27,096, page 16, column 6]—Wigan is a former coal-mining centre in Lancashire, England:

NO MORE WILL ‘KNOCKER-UP’ HAVE TO RISE AT 3.30 A.M.

Last of a long line of knockers-up, 62-year-old Mrs. Gladys Atherton, of Wesley Mesnes, Wigan, pictured from the customer’s side of the window, has decided to retire. For 18 years she has made her living by being the earliest riser in the district, travelling around the neighbouring streets and tapping on windows with her padded staff to make sure scores of miners, railwaymen and factory workers got up in time for work. But now Mrs. Atherton’s days of 3.30 a.m. rising are over. She feels she is getting too old for the job.

The words knocker-up and knocking-up originated in the verb to knock somebody up, meaning: to awaken somebody by knocking at the door or at the window. This verb was used, for example, by the English poet Alexander Pope (1688-1744) in the following from The First Epistle of the Second Book of Horace, Imitated (London: Printed for T. Cooper, 1737) [page 14]:

Time was, a sober Englishman wou’d knock
His servants up, and rise by five a-clock,
Instruct his Family in ev’ry rule,
And send his Wife to Church, his Son to School.

These are, in chronological order, the earliest occurrences that I have found of the words knocker-up and knocking-up used of a person who went round the streets in the early morning to awaken factory hands:

1-: From Household Words. A Weekly Journal. Conducted by Charles Dickens (London, England) of Saturday 17^th August 1850 [Vol. 1, No. 21, page 501, column 2, & page 502, column 1]:

CHIPS.
THE KNOCKING-UP BUSINESS.

NEW wants are being continually invented, and new trades are, consequently, daily springing up. A correspondent brings to light a novel branch of the manufacturing industry of this country, which was revealed to him in Manchester. Lately, he observes, I was passing through a bye-street in Manchester, when my attention was attracted by a card placed conspicuously in the window of a decent-looking house, on which was inscribed, in good text,
“KNOCKING UP DONE HERE AT 2D. A WEEK.”
I stopped a few moments to consider what it could mean, and chose out of a hundred conjectures the most feasible, namely:—that it referred perhaps to the “getting up” of some portion of a lady’s dress, or knocking up some article of attire or convenience in a hurry. I asked persons connected with all sorts of handicrafts and small trades, and could get no satisfaction. I therefore determined to enquire at the “Knocking up” establishment itself. Thither, accordingly, I bent my steps. On asking for the master, a pale-faced asthmatic man came forward. I politely told him the object of my visit, adding, that from so small a return as 2d. a week, he ought to get at least half profit. “Why, to tell you the truth, Sir,” rejoined the honest fellow, “as my occupation requires no outlay or stock in trade, ’tis all profit.” “Admirable profession!” I ejaculated. “If it is no secret, I should like to be initiated; for several friends of mine are very anxious to commence business on the same terms.”
Not having the fear of rivalry before his eyes, he solved the mystery without any stipulations as to secrecy or premium. He said that he was employed by a number of young men and women who worked in factories, to call them up by a certain early hour in the morning; for if they happened to oversleep themselves and to arrive at the mill after work had commenced, they were liable to the infliction of a fine, and therefore, to insure being up in good time, employed him to “knock them up” at two-pence a week.
On further enquiry, he told me that he himself earned fourteen shillings per week, and his son—only ten years old—awoke factory people enough to add four shillings more to his weekly income. He added, that a friend of his did a very extensive “knocking up” business, his connexion being worth thirty shillings per week; and one woman he knew had a circuit that brought her in twenty-four shillings weekly.
There is an old saying, that one half the world does not know how the other half live. I question whether ninety-nine hundredths of your readers will have known till you permit me to inform them how our Manchester friends, in the “Knocking up” line, get a livelihood.

2-: From a review of the above-quoted article published in Household Words. A Weekly Journal. Conducted by Charles Dickens (London, England) of Saturday 17^th August 1850—review published in The Kilkenny Journal, and Leinster Commercial and Literary Advertiser (Kilkenny, County Kilkenny, Ireland) of Saturday 7^th September 1850 [Vol. 18, No. 218, page 2, column 2]:

This may be very new to Mr. Dickens; but to some in Ireland it is old enough. In Belfast, many have no other support than what they derive from the ‘knocking up’ business there. We recollect once seeing a “will,” or something which one of these humble knockers-up intended for a will, by which, on his death-bed, he desired to convey his interest in five or six streets, convenient to a large mill, to another—the conditions being that he would be decently buried, and that an infirm wife would be paid weekly 2s. while the new “knocker-up” held the “contract.” The new comer was acknowledged as if he were a representative of the law, and netted 14s a week, on an average: the winter months being nearly fourfold more profitable than the summer light mornings.

3-: From Whitsuntide Festivities, published in the Manchester Examiner and Times (Manchester, Lancashire, England) of Saturday 7^th June 1851 [Vol. 3, No. 271, page 5, column 6]—the noun calling is in italics in the original text:

Whitsuntide belongs, in Lancashire, to all classes; not only to excursionists with purses, but also to mill hands without purses, and rich and poor meet together, if not in body, yet always in the resolve to enjoy the season. Now the factory-girl hears the “knocker-up” tap his stick at her garret window, and for once in the year thinks him respectable, and is inclined to look leniently on the nature of his calling.

4-: From a transcript of the statement made by Thomas Moores, policeman, during the inquest on the death of Margaret Wheeldon, who was beaten to death in a cellar, published in the Manchester Examiner and Times (Manchester, Lancashire, England) of Saturday 26^th July 1851 [Vol. 3, No. 285, page 6, column 6]:

About twenty minutes to five on Monday morning, while on duty on Back Irwell-street, I heard a scuffle in cellar No. 17, as though some people were fighting. […] I sent an old woman, a knocker-up, who was passing at the time, to fetch a constable.

5-: From Local News, published in the Manchester Examiner and Times (Manchester, Lancashire, England) of Saturday 15^th May 1852 [Vol. 4, No. 369, page 5, column 2]:

Destruction of a Provision Shop.—At six minutes past five o’clock, on Thursday morning, an alarm reached the police station, Clarence-street, through a constable, who brought word that the shop of Mr. Yoxall, provision dealer, in Chester Road, Hulme, was in flames […]. The fire’s discovery was made by a policeman and a “knocker-up,” who, passing near the shop, observed smoke venting itself over the shop-door. They did all they could to arouse the inmates; but it was not till the knocker-up had thrust his official wand through the window of the second storey, that the inmates of the room (Mr. Yoxall, his wife, and a child) were aroused to a sense of their critical situation. Very soon after they had made their escape, the floor of that room fell in.