Origin: 1470–80; < ML (Geoffrey of Monmouth) Uthyrpendragun Uther Pendragon, taken as Medieval Welsh pen(n) head + *dragun < LL dracōnēs, pl. of dracō military standard, L: serpent, dragon(hence, chief or head standard), though the compound is unattested in Welsh sources outside of translations of Geoffrey of Monmouth
"Welsh warlord" (mainly known now in Arthurian Uther Pendragon), 1470, title of a chief leader in war of ancient Britain or Wales, from pen "head" + dragon (q.v.), which figured on the standard of a cohort.