pioneer (n.)

1520s, "one of a party or company of foot soldiers furnished with digging and cutting equipment who prepare the way for the army," from French pionnier "foot-soldier, military pioneer," from Old French paonier "foot-soldier" (11c.), extended form of peon (see pawn (n.2)).

Figurative sense of "a first or early explorer, person who goes first or does something first" is from c. 1600. Related: Pioneers.