c. 1300, rejoisen, "to own (goods, property), possess, enjoy the possession of, have the fruition of," from Old French rejoiss-, present participle stem of rejoir, resjoir "gladden, rejoice," from re-, which here is of obscure signification, perhaps an intensive (see re-), + joir "be glad," from Latin gaudere "rejoice" (see joy).
From mid-14c. in a transitive sense of "make joyful, gladden." Intransitive meaning "be full of joy" is recorded from late 14c. Middle English also used simple verb joy "to feel gladness; experience joy in a high degree" (mid-13c.) and rejoy (early 14c.). Also in 15c.-16c. "to have (someone) as husband or wife, to have for oneself and enjoy." To rejoice in "be glad about, delight in" is from late 14c. Related: Rejoiced; rejoicing.