Arc
late Middle English (denoting the path of a celestial object, especially the sun, from horizon to horizon): via Old French from Latin arcus ‘bow, curve’.
wiktionary
From Middle English ark, from Old French arc, from Latin arcus(“a bow, arc, arch”). Doublet of arch, arco, and arrow.
etymonline
arc (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." Electrical sense is from 1821.
arc (v.)
1882, in the electrical sense, from arc (n.). Meaning "to move in an arc" is attested by 1940. Related: Arced; arcing.
