dex·ter¹ / ˈdekstər/ • adj. archaic & Heraldry of, on, or toward the right-hand side (in a coat of arms, from the bearer's point of view, i.e., the left as it is depicted). The opposite of sinister.dex·ter² • n. an animal of a small, hardy breed of Irish cattle.

dexter (her.) right-hand. XVI. — L. dexter, compar. formation, f. IE. base seen also in Gr. dexiós on the right hand (with Indo-Iran., Balto-Slav., Gmc., Celt., and Alb. cogns.); the primary meaning passes sometimes into ‘adroit’.
So dexterity XVI. — F. — L. Hence dext(e)rous XVII.

dexter in heraldry, of, on, or towards the right-hand side (in a coat of arms, from the bearer's point of view, i.e. the left as it is depicted). The opposite of sinister. The term is recorded from the mid 16th century and comes from Latin, ‘on the right’.