Refers to a craftsman who makes armor, particularly traditional Japanese armor (甲冑).
He was born into a family of famous armorers.
This armor was made by an Edo-period armorer.
鍛冶屋 is a general blacksmith, whereas 甲冑師 specializes in armor.
Compound of 甲冑 (armor) and 師 (master, specialist). The exact historical derivation is uncertain, but the term follows a common pattern for craftsman titles.