French word fois comes from Proto-Indo-European *weig-, and later Latin vice (In place of, subordinate to.)
*weig- (Proto-Indo-European)
vice (Latin)
In place of, subordinate to.
vices (Latin)
feiz (Old French)
Time; instance; occasion.
foys (Middle French)
Time; occasion; occurrence.
fois (French)
(arithmetic) times, multiplied by. Time, an instance of something happening; a repetition.