galea

Galea, galeae is first declension feminine, and strictly it is the leather helmet, as against cassis, the metal one. Writers stopped keeping the distinction from an early date, so in practice either word does any helmet, and galea is the commoner of the two. It belongs with the rest of a legionary's kit: galea, lorica, scutum, gladius, pilum.

The trap is a look-alike. Medieval Latin has a second galea meaning a galley, the oared warship, borrowed from Greek and unrelated to the helmet. In a naval chronicle galeae are ships; in a battle narrative they are headgear. Nothing but the context separates them. The word left little to the Romance languages beyond technical and heraldic use, where a galea still tops a coat of arms.