1735, "a thrust with a sword," originally a fencing term, shortened from allonge, from French allonger "to extend, thrust," from Old French alongier "to lengthen, make long," from à "to" + Old French long, from Latin longus "long" (see long (adj.)).
"to thrust," as in fencing, 1735 (implied in lunged), from lunge (n.). Sense of "make a sudden forward rush" is from 1821. Related: Lunging.