English
arcsecond
From arc + second.
Proto-Indo-European *h₂erkʷ-
…
Proto-Italic *arkuos
Latin arcus ‘a bow, arc, arch’
Old French arc ‘arch’
Middle English ark ‘the path of the sun across the sky’
English arc
Proto-Indo-European *sekʷ- ‘to follow’
Proto-Italic *sekʷondo-
Latin secundus ‘following’
Old French second
Middle English secunde
English second
Today it means
noun A unit of angle; 1/60th of an arcminute, or 1/3600th of a degree.
Language periods are conventional ranges, not dates for this word.
Etymograph / arcsecond