From 'aman; established, i.e. (figuratively) trusty; also (abstractly) trustworthiness -- faith(-ful), truth.
see HEBREW 'aman
H529. emun
אֵמֻן noun [masculine] trusting, faithfulness (on formation compare Ges§ 84a R. 12). 1. 1 בָּם אֵמֻן לֹא בָּנִים children in whom there is no trusting Deuteronomy 32:20 (poetry) 2. אֱמוּנִים plural abstract faithfulness; א ׳צִיר messenger of faithfulness, trusty messenger Proverbs 13:17; א ׳עֵד faithful witness 14:5; compare א ׳אִישׁ 20:6; א ׳שֹׁמֵר keeping faithfulness Isaiah 26:2, perhaps also Psalm 31:24 א ׳נצד see I. [ אָמַן].