The name, originally "Sin Caja", means "without coffin" in Spanish and may refer to the grim aftermath of the Turkey Creek Indian Battle, which was fought a short distance west of the hill in December 1872. The fight developed after raiding Indians had stolen livestock, chased young rancher Andrew Tullis, and dragged a herder to death at the J. Campbell place.
The day following the killing, 13 ranchers from Oakville overtook the band at Turkey (now "Hill") Creek. Five Indians were slain, while one white man, Sebastian Beall, had a tooth shot out. Others in the fight were Caleb Coker, Tim Cude, John Edwards, Bob and Sam Nations, Tobe Odom, Cullen Sanders, Andrew and Woodie Tullis, Rans Tullos, Pleas Waller, John Wilson. The bones of the warriors, put in a cave in San Caja Hill, later mysteriously disappeared. They were supposedly removed by members of the same tribe.
Legends of treasure also hinge upon the name of the hill, for "Caja" can mean "box" or "chest. " This is thought to refer to money hidden in boxes here by Mexican bandits who raided wagon trains and stages traveling on the nearby Laredo-Goliad Road. Other tales tell of silver from the rich San Saba mines once buried nearby, but now lost to history.