"laborer on a canal or railway," 1832, colloquial shortening of navigator (q.v.) in its sense of "one who digs navigation canals."
Entries linking to navvy
navigator n.
1580s, "one who navigates, one who directs the course of a ship," from Latin navigator "sailor," agent noun from navigat-, stem of navigare "to sail, sail over" (see navigation). Meaning "laborer employed in excavating a canal" is by 1775, from sense in inland navigation "communication by canals and rivers" (1727), later extended to those engaged in making railroads. In England, navigation was used in the sense of "an artificial waterway, or a part of a natural one that has been made navigable" by 1720.