mid-15c. "of or pertaining to the law," from L. legalis "legal, pertaining to the law," from lex (gen. legis) "law," possibly related to legere "to gather," on notion of "a collection of rules" (see lecture). Sense of "permitted by law" is from 1640s. The O.Fr. form was leial, loial (see leal, loyal). Related: Legality. Legal tender is from 1740.