What's the meaning of the phrase 'Knocked up'?
Euphemism for pregnant.
What's the origin of the phrase 'Knocked up'?
The 'impregnate' meaning of 'knock up' was coined in the USA in the late 19th century. There is of course another meaning to 'knock up', which is 'awaken someone by knocking'. This second meaning isn't widely used in America, although it is still commonplace in Britain. I can recall that, in my youth in the Black Country district of the English West Midlands, 'knocker's up' were men who, early in the morning, went round to the houses of factory workers and knocked on their bedroom windows to make sure they got up and got ready for work. This was later (in the 1960s) replaced by a loud factory hooter known as a 'bull'.
So, both meanings of 'knock up' involve bedrooms, although "I knocked up my Aunt Jenny this morning" would get a titter in the USA but pass unnoticed in the UK.
Also, there is a further 'assemble quickly' meaning of 'knock up', as in "I knocked up a batch of pancakes for lunch".
When phrases have been coined 'knock' is one of the English that has been called on often. We have:
knock about - beat up
knock about with - be the companion of
knock back - rebuff
knock down - to fell to the ground
knock down price - inexpensive
knock heads together - force a reconciliation
knock back - drink rapidly
knock off - steal
knock oneself out - make a determined effort
knock one's head against - fail to make progress
knock on the head - give up an enterprise
knock on - advance in age
knock over - to overthrow or steal from
knock together - assemble hastily
These were just knocked off quickly (there's another) - I'm sure there are many more.