The story
- Old English · inherited fromġetrēowfull“faithful, holding the faith”
- Middle English · inherited fromtruful
- English todaytrueful
From Middle English truful, trewful, trewfull, from Old English ġetrēowfull (“faithful, holding the faith”), equivalent to true + -ful.
Etymology from Wiktionary, CC BY-SA 4.0.