The Right Honorable William Hupy raised another interesting question in an e-mail to me today. In his words, “Testament, testate, testator and the feminine equivalent testatrix, testimony and testis! [Emphasis mine.] What do all of the former words have to do with the latter if anything? According to my dictionary, testis is the root word and even there, the Latin origin is shown with the meaning of ‘witness’.”
We know the answers to some of the questions surrounding these words but not all. Testimony comes from Latin testimonium,”made up of testis “witness” and, possibly, a noun from monere “to remind.” Testis in the sense of “witness”, comes from the same root as Latin tri “three,” also the origin of English three. Testis was originally a compound noun rather like *tri-sta-i- meaning, roughly, “third person standing by,” with the *sta- root found in English stand and stead.
How the meaning of the Latin word testis wandered off to its other meaning, the one English borrowed, is one of the great unsolved mysteries of etymology. The funniest theory is that the Romans placed their right hands on their testicles and swore by them before giving testimony in court. Cute but no evidence. Another speculation is that we are dealing here with two words coincidentally spelled identically, testis in the sense we use it, coming from testa “pot, shell”, also the source of French tête “head”. More convincing but still pure speculation with no analogies of the sound changes required.
So, history bears no witness to the connections between the family jewels and witnesses—which is always more fun since we are allowed to concoct whatever relatively reasonable etymologies as please us.