All four words refer to places where things are kept, but they differ greatly in size and purpose. 'Storeroom' and 'storage room' mean the same thing — a room inside a building for items not needed daily — and can be used interchangeably. 'Warehouse' describes a very large building, often separate from offices or homes, used for storing goods in large quantities for a business. 'Closet' is much smaller, usually a built-in cupboard in a bedroom or hallway. 'Pantry' is a small room or cupboard reserved for food and cooking items. For everyday household storage, use 'storeroom' or 'storage room'; for a company's goods, use 'warehouse'; for clothes or linens, use 'closet'; and for canned food or dry ingredients, use 'pantry'.
Formed by combining 'store' (from Latin 'instaurare' meaning to set up or restore, via Old French 'estore') with 'room' (from Old English 'rum' meaning space or chamber). The compound 'storeroom' has been in use since the 1600s.