Wikipedia has this:
The place-name Penistone is first attested in the Domesday Book of 1086, where it appears as Pengestone and Pangeston. Penistone is situated on a high ridge, which is believed to be the source of its name.[3] Penistone derives from penn in Old Welsh, which means head, end, top, height or hill, and the Old English ing, a place-name forming suffix and tun, an enclosure, farmstead, village or estate. It most likely means a farm or village at or called Penning