a Brythonic (Celtic) word for "head;" common in place names in Cornwall and Wales (such as Penzance; see also pendragon and Pennsylvania).
Entries linking to pen-
Penzance
place in Cornwall, Pensans (late 13c.), literally "Holy Headland," from Cornish penn "head" + sans "holy."
pendragon n.
"Welsh warlord" (mainly known now via Arthurian romances as the title of Uther Pendragon), late 15c., title of a chief leader in war of ancient Britain or Wales, who were invested with dictatorial powers in times of great danger, from pen "head" (see pen-) + dragon, which figured on the standard of a cohort.