The story
- Old English · derived fromCrīst, Crist
- English todayCrist
Apparently from Old English Crīst, Crist (the vowel may originally have been long in early OE, with subsequent shortening in late OE, see Notes for Christmas on the OED.com website), possibly applied as a nickname for someone who played the part of Christ in a pageant, or alternatively a pet form of the personal names Christian or Christopher.
Etymology from Wiktionary, CC BY-SA 4.0.