Born on July 11, 1898, Lassa was Native American and a member of the Pend d'Orielle tribe, one of three members of the confederated tribes of the Flathead reservation in Montana. He was given the name, Long Time Sleep, by his teammates because he was difficult to wake up in the morning.

Lassa attended and played college football at the Carlisle Indian School and Haskell Institute. Lassa eventually played in the National Football League in 1922 with the Oorang Indians.