"equipped for battle," early 13c., past-participle adjective from arm (v.).
Entries linking to armed
arm v.
"furnish with weapons," c. 1200, from Old French armer "provide weapons to; take up arms," or directly from Latin armare "furnish with arms," from arma "weapons," literally "tools, implements" of war (see arm (n.2)). The intransitive sense of "provide oneself with weapons" in English is from c. 1400. Related: Armed; arming.
unarmed adj.
c. 1300, "with armor removed," from un- (1) "not" + armed, or else past-participle adjective from unarm "strip of armor" (c. 1300), from un- (2) "opposite of" + arm (v.). Meaning "not fitted to attack, weaponless" is from late 14c.