Meaning

adverb in accordance with truth or fact or reality

adverb by right

adverb with sincerity; without pretense

originFrom Middle English truely, treuly, treuli, trewely, treoweliche, treowliche, from Old English trēowlīċe (“faithfully; truly”), equivalent to true + -ly. Cognate with Dutch trouwelijk, Middle Low German truwlike, German treulich, Swedish trolig, Icelandic trygglega.

Etymology from Wiktionary, CC BY-SA 3.0