In the Brave New Words blog, B. J. Epstein today quotes Jonathan Margolis to the effect that translators of the Bible have been euphemistic, using the word thigh instead of penis:
“Generally speaking, when Bible translators have happened upon sexual references, they have been assiduous in seeking out neutralizing euphemisms like men with a mission to protect unborn generations of virginal Sunday School teachers. Thus is ‘penis’ changed in every instance to ‘thigh’. ‘Put, I pray thee, thy hand under my thigh,’ Abraham asks his servant in Genesis, ‘and I will make thee swear by the Lord, the God of heaven, and the God of earth.’ (This is a reference to the custom of ‘testifying’, by which anyone taking a vow places their hand on their testicles.”
A commenter points out that the Bible itself has the euphemism. Is it true that thigh stood for penis? My BS detectors started humming when I saw that old chestnut that testify and testimony are related to the old custom of putting one’s hand on one’s penis (if present) as a form of swearing an oath (the commenter, ‘Anonymous’, actually refers to putting one’s hand on someone else’s penis).
Here’s one internet correction via Random House:
Let’s start with the Latin root since that’s where both of these words come from. The Latin word testis originally meant ‘witness’. It comes from the Indo-European roots *tre- meaning ‘three’ and *sta- meaning ‘stand’. A witness was ‘a third person standing by’. From that came the verb testificare ‘to bear witness’, which evolved into Middle English testify in the fourteenth century.
Where it gets confusing is that testis also — although not originally — meant testicle in Latin. The English word testicle comes from Latin testiculus, a diminutive of testis, and first appeared in the fifteenth century. If testis meaning ‘witness’ and testis meaning ‘testicle’ are indeed the same word, then the etymology could be that the testicles are ‘witness’ or evidence of virility.
There is more, including a summary of the OED, which I have just looked at myself (thus discovering that testicles was once also used to refer to the tonsils – I do have those). The article concludes on the suspicion that the Bible passage quoted above may well be the source of this confusion:
My Biblical expert says that this ritual seems to come from the idea that the thigh is the locus of power, probably because it’s near the genitals. He also notes that some modern interpreters of the Bible envision it as a swearing on the genitals, with “under the thigh” being a euphemism which goes all the way back to the Hebrew.
I think it is very likely that these Biblical passages are the source of the popular notion that testify derived from testicle.