Amen to using Hebrew Bible and Christian Bible or Hebrew Scriptures and Greek Scriptures rather than "old" and "new" (even though Lewis Black uses these terms in the worst possible way in one of his routines).

Alas, however, the idea of testament coming from two men putting their hands on each other's testicles is not true. Testis is Late Latin for witness. There is a relationship between testify and testicle but it's not about grabbing private parts to seal the deal. There was, in the Hebrew Scriptures, swearing by "grasping the thigh" (a likely euphemism), but that's not the connection. Seems that the ancient Romans just thought that the testis was a "witness" to a man's virility.