Origin and history of testification

late 14c., testifien, "give legal testimony, affirm the truth of, bear witness to" (transitive); of things, c. 1400, "serve as evidence of;" from Anglo-French testifier, from Latin testificari "bear witness, show, demonstrate," also "call to witness," from testis "a witness, one who attests" (see testament) + combining form of facere "to make, to do" (from PIE root *dhe- "to set, put").

The notion is to communicate to others the reality of some thing not known to them. The historical etymology of this word is unlikely to be related to that of testes (see testis).

The intransitive Biblical sense of "openly profess one's faith and devotion" is attested from 1520s and has been preserved in evangelical language. Related: Testified; testifying; testifier.