An Etymological Dictionary of Astronomy and Astrophysics

A line that deviates from straightness in a smooth, continuous fashion. A line representing a variable on a graph.

Etymology (EN): From L. curvus “crooked, curved, bent;” cf. Av. skarəna- “round,”
Gk. kirkos, krikos “a ring;” PIE base *sker- “to turn, bend.”

Etymology (PE): Xam, variant kamân “arc,” Mid.Pers. kamân, probably from PIE *kamb- “to bend, crook,” cf. Breton kamm “curved, bent.”