Why is the ninth month called September?
"pledge," c.1300, from Old French gage "pledge (of battle), security, guarantee" (11c.), from Frankish *wadja-, from Proto-Germanic *wadi- (see wed). Italian gaggio, Spanish and Portuguese gage are French loan-words. The verb is late 15c., from French gager. Related: Gaged, gaging.
see gauge. "The spelling variants gauge and gage have existed since the first recorded uses in Middle English, though in American English gage is found exclusively in technical uses" [Barnhart]. Related: Gaged; gaging.