Word Origin & History
(pl. testes), 1704, from L. testis "testicle," usually regarded as a special application of testis "witness" (see testament
), presumably because it "bears witness" to virility (cf. Gk. parastates, lit. "one that stands by;" and Fr. slang témoins, lit. "witnesses").
But Buck thinks Gk. parastatai "testicles" has been wrongly associated with the legal sense of parastates "supporter, defender" and suggests instead parastatai in the sense of twin "supporting pillars, props of a mast," etc. Walde, meanwhile, suggests a connection between testis and testa "pot, shell, etc."