"equipped for battle," early 13c., past-participle adjective from arm (v.).

also arə-, Proto-Indo-European root meaning "to fit together."

It forms all or part of: adorn; alarm; aristarchy; aristo-; aristocracy; arm (n.1) "upper limb of the body;" arm (n.2) "weapon;" armada; armadillo; armament; armature; armilla; armistice; armoire; armor; armory; army; art (n.) "skill as a result of learning or practice;" arthralgia; arthritis; arthro-; arthropod; arthroscopy; article; articulate; artifact; artifice; artisan; artist; coordination; disarm; gendarme; harmony; inert; inertia; inordinate; ordain; order; ordinal; ordinance; ordinary; ordinate; ordnance; ornament; ornate; primordial; subordinate; suborn.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit irmah "arm," rtih "manner, mode;" Armenian arnam "make," armukn "elbow;" Greek arti "just," artios "complete, suitable," artizein "to prepare," arthron "a joint;" Latin ars (stem art-) "art, skill, craft," armus "shoulder," artus "joint," arma "weapons;" Old Prussian irmo "arm;" German art "manner, mode."

late 14c., "deprive of power to injure or terrify, render harmless," a figurative sense, from Old French desarmer (11c.), from des- "reverse of" (see dis-) + armer "to arm" (see arm (v.)). The literal senses "deprive of weapons" (transitive), "put off one's armor or lay down one's weapons" (intransitive) are early 15c. Related: Disarmed; disarming; disarmingly.

"prepare for an attack," 1590s, from fore- + arm (v.) "take up weapons." Related: Forearmed; forearming.

also re-arm, "provide with a new supply of weapons; acquire a new supply of weapons," 1805 (implied in rearming), from re- "back, again" + arm (v.) "to take up arms; supply with arms." In 20c., especially "to acquire more advanced weapons." Related: Rearmed.

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.

burrowing mammal of the American tropics, 1570s, from Spanish armadillo, diminutive of armado "armored," from Latin armatus, past participle of armare "to arm, furnish with weapons," from arma "weapons" (including defensive armor), literally "tools, implements (of war);" see arm (n.2). The animal is so called for its hard, plated shell.

1650s, "naval force equipped for war," from Latin armamentum "implement," from Latin armare "to arm, furnish with weapons" from arma "weapons" (including defensive armor), literally "tools, implements (of war);" see arm (n.2). The meaning "process of equipping for war" is from 1813.

c. 1400, "an armed force," from Latin armatura "armor, equipment," from armatus, past participle of armare "to arm, furnish with weapons" from arma "weapons," literally "tools, implements (of war);" see arm (n.2). The meaning "armor" is mid-15c.; that of "protective covering of a plant or animal" is from 1660s. The electromagnetic sense is from 1835.

"temporary suspension of hostilities by agreement of the parties," 1707, from French armistice (1680s), coined on the model of Latin solstitium (see solstice), etc., from Latin arma "arms" (see arm (n.2)) + -stitium (used only in compounds), from PIE *ste-ti-, suffixed form of root *sta- "to stand, make or be firm."

The word is attested in English from 1660s in the Latin form armistitium. German Waffenstillstand is a loan-translation from French. Armistice Day (1919) commemorated the end of the Great War of 1914-18 on Nov. 11, 1918, and memorialized the dead in that war. In Britain, after World War II, it merged with Remembrance Day. In U.S. (which had already a Memorial Day for the dead), Armistice Day became a national holiday in 1926; and in 1954, it was expanded to also honor living World War II and Korean War veterans and was re-dubbed Veterans Day.