"Tanis was actually its Greek name. We are told that its ancient Egyptian name was Djanet." From: http://www.touregypt.net/featurestories/tanis.htm
Tanis: Greek from the Phoenician Tanith, meaning "serpent lady"
"In Egyptian, her name means Land of Neith, Neith being a war goddess." More here: Tanit
Thank you! “Tan” seems to refer to a large reptile rather than a whale, so Tanit may have been originally a serpent goddess of the Middle East, the local deity of the city.