The story
- Old French · derived fromnon-
- English todaychalant
A back-formation from nonchalant, itself from Old French non- + chalant (“concerning, bothering”). By this process, the original Old French participle was coincidentally re-formed.
Words from the same roots
Old Frenchnon- all →
non-
Etymology from Wiktionary, CC BY-SA 4.0.