An Etymological Dictionary of Astronomy and Astrophysics

Possessed, experienced, performed, etc., by each of two or more with respect to the other; reciprocal.

Etymology (EN): M.E., from M.Fr. mutuel, from L. mutu(us) “reciprocal, done in exchange,” from PIE base *mei- “to change,” → mutation.

Etymology (PE): Dosuyé from do, → two, + su “side, direction,” from Mid.Pers. sôk “direction, side” + nuance suffix -é.