An Etymological Dictionary of Astronomy and Astrophysics

General: A set, collection or group formed of
members with certain attributes or traits in common.

Etymology (EN): From Fr. classe, from L. classis “summons, division of citizens for military draft, hence army, fleet, also class in general.”

Etymology (PE): Radé “a line, series, row,” from Mid.Pers. ratak “series, row,” O.Pers. râd-, Av. raz- “to direct, put in line, set,” Av. razan- “order.”