You do realise that they mean they are annoyed, not drunk. Yes...but now you've spoiled a good run....Joking...Yes I do...I constantly goad them on language use on our sister site...But then...they say they sometimes have not got a clue what I'm on about....We don't as is oft said share a language...we each have our own version it seems
Knocked up seems to have been an american slang with knock and bang both euphemisms for sex. In Britain the term knocked up can also mean woken up with a knock on the door or window - and a profession of knocker-up. The industrial revolution brought a need for people to wake for shifts and early mornings, before alarm clocks were affordable and reliable. The knocker up was the person with a stick to rap on the bedroom window of the worker. Knockered Up | Now I Know
Imagine this Kentucky farmer's grand dad and a Scottish farmer trying to talk to each other during the war
"Knocked up" was a phrase used frequently in British colloquialism to describe an item quickly constructed or manufactured.....it can also be referred to an organisation or game team quickly established sometimes for an "ad hoc" purpose. Before the alarm clock ......."Knocked Up" has it's origins in the Victorian era when lamplighters extinguishing street gas lighting would also act as "Knockers Up" using their lighting/extinguishing poles to awake up people for work by knocking on bedroom windows. Being "Knocked Off" was also the phrase used frequently (to copulate with) to describe a sexual relationship outside marriage or with single people....usually with the outcome uncertain.
In America knocked off means to be killed by someone. Knock off means to quit working, "I knock off at 5 PM today." As Shedrake said, knock and bang mean sex and knocked up means pregnant.
I think that there are many variables in the English language using "knock".....for overall use from medieval times, the OED should give good examples. Here's a good one as I remember from the days of my youth.... a "Knocking Shop", a building, could be domestic premises or a public house where sexual relationships were casual and were the norm. Hasten to add that respectable ladies did not venture into these places and they were not the place to meet the love of your life.
Abundant examples of the use of "Knock" in the English language in the OED here...covers the US dimension. https://www.oed.com/view/Entry/104090?rskey=vc6KCb&result=1#eid1258343730 For anyone acquainted with internal combustion engines "knocking",the result of engine pre ignition,so named by the continual knocking noise being generated by a defective ignition timing.
Can also mean the opposite from the point of view an engine can have 'big end knock' due to lack of oil circlating through to the bend ends ie the bearings of the pistons where they connect to the crankshaft TD
Another good example TD of faults found and diagnosed with rotating shafts.....a good listen initially with a screwdriver handle to the ear and the drive end to where the noise is coming from. Digressing......From my experience,owning cars, a big end knock is likely to be accompanied by a fall off in engine performance where as a pre ignition knock (also referred to as pinking) tends not to affect performance until the engine overheats,performance deteriorates and causes general engine failure. There are accounts recorded by RAF personnel of acquiring AVGAS 100 Octane to use in car engines which I feel is something of a myth as the car specification would not be designed for AVGAS 100.I would think that use of a car fuelled with AVGAS 100 would soon show signs of knocking,even in the days when fuel for cars was leaded but not to the degree of AVGAS 100.