Etymology
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arm (n.1)

[upper limb of the human body], Middle English arm, from Old English earm, from Proto-Germanic *armaz (source also of Old Saxon, Danish, Swedish, Middle Dutch, German arm, Old Norse armr, Old Frisian erm), from PIE root *ar- "to fit together" (source also of Sanskrit irmah "arm," Greek arthron "a joint," Latin armus "shoulder").

Arm of the sea was in Old English. Arm-twister "powerful persuader" is from 1915. Arm-wrestling is from 1899.

They wenten arme in arme yfere Into the gardyn [Chaucer]
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contact (n.)

1620s, "action, state, or condition of touching," from Latin contactus "a touching" (especially "a touching of something unclean, contamination"), from past participle of contingere "to touch, seize," from assimilated form of com "with, together" (see con-) + tangere "to touch," from PIE root *tag- "to touch, handle."

The figurative sense of "a connection, communication" is attested from 1818. The meaning "a person who can be called upon for assistance" is attested by 1931. As a call to the person about to spin an aircraft propeller to signal that the ignition is switched on, contact was in use by 1913.

To make contact (1860) originally was in reference to electrical circuits. Contact lens " thin artificial lens placed directly on the surface of the eye to correct visual defects" is first recorded 1888, in a translation of an article published in Zurich in 1887 by A. Eugen Fick; contacts for "contact lenses" is from 1957. Contact sport, for one involving bodily contact, is attested from 1922.

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contact (v.)

1834, "to bring together or put in contact," from contact (n.). Meaning "get in touch with" is 1927, American English. Related: Contacted; contacting.

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arm (n.2)

[weapon], c. 1300, armes (plural) "weapons of a warrior," from Old French armes (plural), "arms, weapons; war, warfare" (11c.), from Latin arma "weapons" (including armor), literally "tools, implements (of war)," from PIE *ar(ə)mo-, suffixed form of root *ar- "to fit together." The notion seems to be "that which is fitted together." Compare arm (n.1).

The meaning "branch of military service" is from 1798, hence "branch of any organization" (by 1952). The meaning "heraldic insignia" (in coat of arms, etc.) is early 14c., from a use in Old French; originally they were borne on shields of fully armed knights or barons. To be up in arms figuratively is from 1704; to bear arms "do military service" is by 1640s.

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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.

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yard-arm (n.)

also yardarm, 1550s, from yard (n.2) in the nautical sense (attested from Old English) + arm (n.1). In 19c. British naval custom, it was permissible to begin drinking when the sun was over the yard-arm.

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strong-arm (adj.)

"using physical force," 1897, from noun phrase (c. 1600), from strong (adj.) + arm (n.). As a verb from 1903. Related: Strong-armed; strong-arming.

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arm-band (n.)

"band or bracelet for the arm," by 1782; see from arm (n.1) + band (n.1).

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arm-rest (n.)

also armrest, "something designed as a rest for the arm," by 1850, from arm (n.1) + rest (n.).

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sidearm (adj.)

also side-arm, "done with the swing of the arm extended sideways," 1908, from side (adj.) + arm (n.1).

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