Middle English helle, going back to Old English hell, helle, going back to Germanic *haljō (whence also Old Saxon hellia "abode of the dead," Old High German hella, hellia, Old Norse hel "abode of the dead, the death goddess," Gothic halja, translating Greek Háidēs), perhaps from an o-grade nominal derivative of the Germanic verbal base *hel- "cover, hide" — more at conceal
Note: The connection with *hel- "conceal" is traditional in the etymological literature, though given that the literal meaning of *haljō, the mythological abode of the dead, is unknown, it must be regarded as speculative.
