bonk [E20th] Bonk is an imitation of the sound of a solid object striking a hard surface, a variant of words such as *bang and bong [M19th]. It is reported to have appeared as a verb, meaning ‘to shell’, in the First World War, but the earliest written record is from 1929. The sexual sense does not seem to have been used before the mid 1970s, but has become established, perhaps because people feel it is an acceptable term that is not too rude. The link with bonkers [M20th], ‘mad’, probably comes from the idea of a mad person having been ‘bonked’ on the head one too many times.