armor

English armor comes from Middle English armure, borrowed from Anglo-Norman armure and Old French armeüre, ultimately from Latin armātūra, a form built on Latin arma, which itself traces back to Proto-Indo-European *h₂(e)rmos, meaning something like a fitting or joint.

The word began with a root about fitting things together, passed into Latin as arma ('equipment' or 'tools'), then became armātūra, and moved through French forms like armeüre before settling into English as armor.

Armor is a doublet of armature and armure, since both descend from the same Latin word, armātūra, by different paths into English.