"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.
1580s, "soldier armed with a lance," from French lancier "soldier, knight armed with a lance," from Old French lance (see lance (n.)).
"heavy-armed foot soldier of ancient Greece," 1727, from Greek hoplites "heavy-armed," as a noun, "heavy-armed soldier, man-at-arms," from hopla "arms and armor, gear for war," plural of hoplon "tool, weapon, implement." One who carries a large shield, as opposed to a peltastes, so called for his small, light shield (pelte).
1826 (adj.), "eight-footed or eight-armed;" 1835 (n.) "an eight-footed or eight-armed animal," especially an octopus, from Latinized form of Greek oktōpod-, stem of oktōpous (see octopus).