game of thrones - Who was the first person to bear the name "Lannister"?

We don't know any Lannister before Lann the clever ( and we don't even know if he was called a Lannister), who founded House Lannister and the first King of the Rock, Loreon I Lannister (Loreon the Lion).

This info is given in the World of Ice and Fire. It is also said (rumored more like it) that Lann had a hundred sons

Lann the Clever supposedly lived to the age of 312, and sired a hundred bold sons and a hundred lissome daughters, all fair of face, clean of limb, and blessed with hair "as golden as the sun.

_{The World of Ice and Fire; The Westerlands.}

Besides these, there is speculation. It is possible that Lann started calling himself a Lannister, or one of his many sons.

We also don't who the parents of Loreon where, so we cannot know for sure if there were other Lannisters before him.