1. English: The surname Hatt may have originated from an Old English personal name like Hata, which means "the one who hates" or "the enemy."
2. German: In some cases, the surname Hatt could be a variant of the German surname Hatten, which is a habitational name derived from a place name.
3. Scandinavian: The surname Hatt may also have Scandinavian roots and could be derived from the Old Norse word "hatt", which means "hat." It is possible that the original bearers of the Hatt surname were hat makers or merchants.
It's worth noting that without specific genealogical research, it can be difficult to determine the precise origin of a particular Hatt surname.