Take the piss
Q From Stephen Balkam: Could you throw some light on to the origin of taking the piss? My (English) wife seemed to think it meant actually being made to drink someone else’s urine.
A Nothing literal about this one, you will be pleased to hear. It’s usually said that the phrase derives from an older one, piss-proud, which refers to having an erection when waking up in the morning, which is usually attributed to a full bladder (proud here being an obvious pun on its senses of something raised or projecting and of something in which one may take satisfaction).
It’s first recorded, as so many such indecorous expressions are, in Francis Grose’s A Classical Dictionary of the Vulgar Tongue; in the second edition of 1788 he wrote: “Piss-proud, having a false erection. That old fellow thought he had an erection, but his — was only piss-proud; said of any old fellow who marries a young wife”.
This developed into a figurative sense of somebody who had an exaggerated idea of his own importance. So to take the piss is to deflate somebody, to disabuse them of their mistaken belief that they are special. It’s not recorded before the beginning of the twentieth century.