Roman men considered that they had sworn an oath if they held their testicles in their hands while swearing. This included the oath to tell the truth before giving testimony in court. Only real men, in swearing on their potency, were expected to tell the truth. The evidence of women and eunuchs was not believed under the law because they could not be fully trusted. The truth could not be expected or known by those who did not possess testicles. Roman culture was phallocentric. Possession of the truth was more assured if one had testicles. Access to logic and command of knowledge was favoured if one had a phallus and, with it, testicles.

It has been suggested that the words testimony and testify originate from testicles. However, they come from test, which means witness, the one who stands by.