The peaks are so named for their resemblance to a woman's breasts. The word "tetas" is colloquial for "breasts" in Spanish, much like the English word "tits".
A common misconception is that Las Tetas are located in the municipality of Cayey. Las Tetas are actually located in the municipality of Salinas, in Barrio Palmas, a ward on the northwestern part of the municipality of Salinas.
Despite all the facts, everybody calls them Las Tetas de Cayey.