Wordorigins.org

Does the word testify (with its associated forms like testimony and testament) come from testicle?

All these words come from the Latin testis meaning witness. The ultimately etymology of the Latin word is uncertain with the usual explanation being that the testes or testicles are witnesses to or prove a man’s virility. Some suggest that the Latin words for the witness and the reproductive organs are unrelated, with testa, meaning pot or shell, being the source for the latter.