Those of Saragossa were most in repute in the days of chivalry.
Close helmet. The complete head-piece, having in front two movable parts, which could be lifted up or let down at pleasure.
Visor. One of the movable parts; it was to look through. Bever, or drinking-piece. One of the movable parts, which was lifted up when the wearer ate or drank. It comes from the Italian verb bevere (to drink)
Morion. A low iron cap, worn only by infantry.
Mahomet's helmet. Mahomet wore a double helmet; the exterior one was called al mawashah (the wreathed garland).
The helmet of Perscus (2 syl.) rendered the wearer invisible. This was the “helmet of Hades,” which, with the winged sandals and magic wallet, he took from certain nymphs who held them in possession; but after he had slain Medusa he restored them again, and presented the Gorgon's head to Athena [Minerva], who placed it in the middle of her aegis.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894