Ban(a)
From Tolkien Gateway
Ban(a) is a Westron word meaning half.
The element is seen in compounds. It usually is followed by an a but it is not known if it belongs to the full form of the word *bana.
Etymology
The word seems to come from and Adûnaic element, like osme root *BAN.
Ad. banâth "wife" means "the half of the couple"