early 14c. "relative freedom of a noble metal from alloy or other impurities," from Anglo-French alai, Old French aloi, from aloiier (see alloy, v.). Meaning " base metal alloyed with a noble metal" is from c.1400. Modern spelling from late 17c.

c.1400, "mix with a baser metal," from Old French aloiier "assemble, join," from Latin alligare "bind to, tie to," compound of ad- "to" (see ad-) + ligare "to bind" (see ligament); hence "bind one thing to another." Related: Alloyed; alloying.