Meaning

noun armor plate that protects the head

noun a protective headgear made of hard material to resist blows

originFrom Middle English helmet, helmett, a borrowing from Old French helmet, heaumet, a diminutive of helme (Modern French heaume), equivalent to helm + -et. The Old French is itself of Germanic origin (whence Old English helm). Used in English since the 15th century, it has largely displaced helm as the general word.

Etymology from Wiktionary, CC BY-SA 3.0