In the UK the expression 'knock you up' doesn't mean 'make you pregnant'. It means 'wake you up' It dates from the days before alarm clocks when people were paid to wake workers up each morning. Some used a long slender pole to tap on bedroom windows others were like this woman, Mary Smith of Brenton Street, who used a pea shooter. They were commonly known as ‘knocker-ups’ or ‘knocker-uppers’. Photograph from Philip Davies’ Lost London: 1870-1945.