1640s, "small number of military men detailed for some purpose," from French esquade, from Middle French escadre, from Spanish escuadra or Italian squadra "battalion," literally "square," from Vulgar Latin *exquadra (see square, n.). Before the widespread use of of automatic weapons, infantry troops tended to fight in a square formation to repel cavalry or superior forces. Extended to sports 1902, police work 1905.