From Old French estalon 'breeding horse kept in a stall,' from Frankish *stall 'stable,' ultimately from Proto-Germanic *stallaz 'standing place.'
An uncastrated adult male horse, especially one kept for breeding.
From Old French estalon (modern French etalon), from Frankish *stall 'stable, stall,' from Proto-Germanic *stallaz 'standing place.' The original sense was a horse kept in a stall — specifically, a male horse maintained in a stable for breeding rather than for riding or draft work. Key roots: *stel- (Proto-Indo-European: "to put, to stand, to place").
French etalon means both 'stallion' and 'standard (of measurement)' — in both cases, the idea is something that stands as a reference or model. A stallion stands at stud as the standard for breeding, and a measurement standard stands as the reference for calibration.