Askance means with a sideways look of doubt or disapproval. Look askance at it, glance askance, regarded askance.
It appears almost only with look or a word like it, and the sideways glance is doing the disapproving. The origin is genuinely unknown despite several plausible candidates. Note askew beside it, which is about crookedness rather than doubt.
1adverbaskanceWith a sideways look of doubt or disapproval.
“The other passengers looked askance at the man eating raw onions on the train.”
askance is a manner of looking.
The origin is unknown. Several sources have been proposed, in Middle English, Old French and Italian, none of them settled.
Italian
a scancio — obliquely
Old French
a escone — hidden
English, today
askance
Built from
unknown. Possibly from Middle English askances (“as if”), or from Old French a escone (“hidden”) or Italian a scancio (“obliquely”). Compare asquint, Middle English askoyn (“at a slant, askance”), Dutch schuin, schuins (“sideways”), schuiven (“to shove”), schuinte (“slope”).
Etymology from Wiktionary, CC BY-SA