Why is an aunt called an aunt?

from Anglo-Fr. aunte, from O.Fr. ante (Mod.Fr. tante, from a 13c. variant), from L. amita "paternal aunt" dim. of *amma a baby-talk or non-I.E. word for "mother" (cf. Gk. amma "mother," O.N. amma "grandmother," M.Ir. ammait "old hag," Heb. em, Arabic umm "mother"). Curreent term is the sister or sister-in-law of your mother or father.
because your dad or mom sister is your aunt that is why an aunt is called an aunt