How did people wake up in the morning before alarm clocks? They paid to get knocked up.
The following passage appears in Charles Dickens’ Great Expectations:
As I was sleepy before we were far away from the prisonship, Joe took me on his back again and carried me home. He must have had a tiresome journey of it, for Mr. Wopsle, being knocked up, was in such a very bad temper
Great Expectations
Where I come from, “being knocked up” means that you’re pregnant. You can imagine my surprise when I read that Mr. Wopsle was somehow expecting a child. It turns out that many workers of 19th and early 20th century Britain were knocked up, most mornings in fact.
Personal mechanical alarm clocks date back as far as the middle of the 19th century, but most working people did not own one. The workers still stayed up late and had to get up early, of course, so they employed professionals to wake them up: the knockers-up.
A knocker-up went door-to-door, physically knocking on people’s front doors or windows in order to rouse them for work. A good knocker-up waited to see if you’d heard the alarm; the efficient ones just rapped and moved on. Some knockers-up used long poles to tap on upstairs windows, so that they didn’t wake the entire household.
The job, as with so many onerous but not physically gruelling tasks, fell mainly to women and elderly men. It did beg one question: just who woke those who woke people up?
We had a knocker-up, and our knocker-up had a knocker-up
Knocker-uppers
And our knocker-up’s knocker-up didn’t knock our knocker up
So our knocker-up didn’t knock us up
‘Cos he’s not up.
[Thanks to Gareth E.]
The Generalist Academy 
