Half Dome was originally called Tis-sa-ack, meaning Cleft Rock in the language of the local Ahwahnechee people. Tis-sa-ack is also the name of the fourth route on the formation, ascended by Royal Robbins and Don Peterson over eight days in October 1969. Tis-sa-ack is the name of a mother from a native legend. The face seen in Half Dome is supposed to be hers. Tis-sa-ack is the name of a Mono Lake Paiute Indian girl in the Yosemite Native American legend. John Muir referred to the peak as Tissiack.. Muir also referred to it as South Dome in his The Yosemite book.