1297, from O.Fr.
comun, from L.
communis "in common, public, general, shared by all or many," from PIE
*ko-moin-i- "held in common," compound adjective formed from
*ko- "together" +
*moi-n-, suffixed form of base
*mei- "change, exchange" (see
mutable), hence lit. "shared by all." Second element of the compound also is the source of L.
munia "duties, public duties, functions," those related to
munia "office." Perhaps reinforced in O.Fr. by Frank. descendant of P.Gmc.
*gamainiz (cf. O.E.
gemæne "common, public, general, universal"), from the P.Gmc. form of PIE
*ko-moin-i- (see
mean (adj.)). Used disparagingly of women and criminals since c.1300.
Commons "the third estate of the English people as represented in Parliament" is from 1377.
Common sense is 14c., originally the power of uniting mentally the impressions conveyed by the five physical senses, thus "ordinary understanding, without which one is foolish or insane" (L.
sensus communis, Gk.
koine aisthesis); meaning "good sense" is from 1726.
Common pleas is 13c., from Anglo-Fr.
communs plets, hearing civil actions by one subject against another as opposed to pleas of the crown.
Common prayer is contrasted with private prayer.