The word dragon entered the English language in the early 13th century from Old French dragon, which, in turn, comes from the Latin: draco (genitive draconis) meaning "huge serpent, dragon", from Ancient Greek δράκων, drkōn (genitive δράκοντος, drkontos) "serpent".[4][5] The Greek and Latin term referred to any great serpent, not necessarily mythological.[6] The Greek word δράκων is most likely derived from the Greek verb δέρκομαι (drkomai) meaning "I see", the aorist form of which is ἔδρακον (drakon).[5] This is thought to have referred to something with a "deadly glance",[7] or unusually bright[8] or "sharp"[9][10] eyes, or because a snake's eyes appear to be always open; each eye actually sees through a big transparent scale in its eyelids, which are permanently shut. The Greek word probably derives from an Indo-European base *derḱ- meaning "to see"; the Sanskrit root दृश् (dr̥ś-) also means "to see".[11]