Arsenal Stash is a term used to describe a collection of weapons and ammunition. The two words that make up the term are 'ARMS' and 'AMMO', both of which have four letters. ARMS refers to any type of weapon, such as guns, knives, swords, or bows and arrows, while AMMO refers to the ammunition used in these weapons, such as bullets, arrows, or shells. Together, they form a term that describes a collection of weapons and ammunition.