pendragon (n.)

a Brythonic (Celtic) word for "head;" common in place names in Cornwall and Wales (such as Penzance; see also pendragon and Pennsylvania).

mid-13c., dragoun, a fabulous animal common to the conceptions of many races and peoples, from Old French dragon and directly from Latin draconem (nominative draco) "huge serpent, dragon," from Greek drakon (genitive drakontos) "serpent, giant seafish," apparently from drak-, strong aorist stem of derkesthai "to see clearly," from PIE *derk- "to see" (source also of Sanskrit darsata- "visible;" Old Irish adcondarc "I have seen;" Gothic gatarhjan "characterize;" Old English torht, Old High German zoraht "light, clear;" Albanian dritë "light").

Perhaps the literal sense is "the one with the (deadly) glance." The young are dragonets (c. 1300). Fem. form dragoness is attested from 1630s. Obsolete drake (n.2) "dragon" is an older borrowing of the same word, and a later form in another sense is dragoon. Used in the Bible generally for creatures of great size and fierceness; it translates Hebrew tannin "a great sea-monster," and tan, a desert mammal now believed to be the jackal.