arch n.

late 14c., "part of a curved line," originally in reference to the sun's apparent motion across the sky, from Old French arc "bow, arch, vault" (12c.), from Latin arcus "a bow, arch," from Proto-Italic *arkwo- "bow."

This has Germanic cognates in Gothic arhvazna, Old English earh, Old Norse ör "arrow," from Proto-Germanic *arkw-o- "belonging to a bow." It also has cognates in Greek arkeuthos, Latvian ercis "juniper," Russian rakita, Czech rokyta, Serbo-Croatian rakita "brittle willow." De Vaan sees an Italo-Germanic word for "bow" which can be connected with Balto-Slavic and Greek words for "willow" and "juniper" "under the well-founded assumption that the flexible twigs of juniper or willow were used as bows." The Balto-Slavic and Greek forms point to *arku-; "as with many plant names, this is likely to be a non-IE loanword."

The electrical sense is attested from 1821.

[strung, elastic weapon for shooting arrows] Middle English boue, from Old English boga "archery bow; anything bent or arched, an arch, a rainbow," from Proto-Germanic *bugon (source also of Old Norse bogi, Old Frisian boga, Dutch boog, German Bogen "bow"), from PIE root *bheug- "to bend," with derivatives referring to bent, pliable, or curved objects.

The sense of "a looped knot," especially an ornamental one, is from 1540s. The musician's bow (1570s) formerly was curved like the archer's.

The former popularity of the longbow as a characteristic English weapon is attested in expressions such as bow-legged; to have the bent of (one's) bow "know one's intentions or inclinations" (1560s), to shoot in (another's) bow "practice an art other than one's own;" bow-hand "the left hand," hence "on the wrong side, inaccurately;" have two strings to (one's) bow "have more than one means to accomplish something;" draw the long bow "exaggerate, lie."