UNCLE, the brother of a person's father or mother, also the husband of one's aunt (i.e. the sister of a father or mother). The French one le, which appears in Anglo-French as uncle, comes from a Late Latin unculus, a shortened form of the Latin avunculus, a maternal uncle, the brother of one's mother. The word is a diminutive of avus, grandfather. The Latin for a paternal uncle is patruus. " Aunt" comes through the Old French aunte, ante, corrupted into the modern tante, from Latin amita, a father's sister, a paternal aunt, the maternal aunt being called matertera.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)