Credible means able to be believed. A credible witness, a credible threat, hardly credible.
It is about the claim rather than the person, which is what separates it from credulous, meaning too ready to believe, and the two are confused constantly. A credible threat is one taken seriously enough to act on.
1adjectivecredibleAble to be believed.
“The jury didn't find her story credible because it kept changing.”
credible is a quality.
Latin credibilis comes from credere, to believe.
Proto-Indo-European
*ḱerd-
Latin
crēdibilis — worthy of belief
Middle French
credible
Middle English
credible
English, today
credible
Built from
From Middle English credible, borrowed from Middle French credible, from Latin crēdibilis (“worthy of belief”), from crēdō (“believe”); see credit.
Etymology from Wiktionary, CC BY-SA