As I understand it, in Chinese, ‘turtle head’ (pronounced QUAY-toe in Mandarin) is a common term used to describe the male appendage, because it is said to look and sound like a penis (some turtles emit a hissing sound when they withdraw their head into their shell).
I would like to know if ‘turtle head’ is, in fact, the actual medical term for the penis, or if it is just a common slang expression for the penis like ‘cock’ or ‘pecker.’ In other words, if you were to attend a conference of Chinese urologists, would you hear them talking about ‘turtle heads’?
While I don’t dispute common usage, it seems, from what I gather, that gui tou is used seriously to refer to the glans.
For example, this page, from a hospital’s site talks about inflamation of the glans and foreskin as 包皮龟头炎.
However, when I was a teen, in French, the proper word for “glans”, “gland”, was a relatively common insult. So a word can both be harsh slang and a proper medical term.
I’ve been told that calling someone a “turtle egg” is a big insult in Chinese because it’s basically a way to call someone a bastard (turtles don’t know who their parents are). A college prof who was fluent in Chinese once said during a lecture that telling someone to “Roll away” [like a turtle egg] in Chinese was like saying “fuck off.”