testament

\ \ [13] Testament is one of a range of English words that go back to Latin testis ‘witness’. This was derived from a prehistoric Indo-European base *tris- ‘three’, and so denoted etymologically a ‘third person’, who was not party to an agreement and thus could be a disinterested witness to it. Other English members of the testis family include testicle [15] (which etymologically ‘bears witness’ to a man’s virility), testify [14], testimony [14], and the prefixed forms attest [16], contest, detest, intestate [14], and protest. The use of testament for ‘will’ was inspired by the notion of a ‘witnessed’ document. Its application to the two parts of the Bible arose from a mistranslation of Greek diathékē, which meant both ‘covenant’ and ‘will, testament’. It was used for the ‘covenant’ between God and human beings, but Latin translators rendered it as if it were being used for ‘will’ rather than ‘covenant’.

\ \ Cf.⇒ ATTEST, CONTEST, DETEST, INTESTATE, PROTEST, TESTICLE, TESTIFY, TESTIMONY, THREE