The story
The noun is derived from stock (“supply of anything ready for use”) + pile (“mass of things heaped together”). The verb is derived from the noun.
Etymology from Wiktionary, CC BY-SA 4.0.
stockpile
stock·pileToday it means: A supply (especially a large one) of something kept for future use, specifically in case the cost of the item increases or if there a shortage. Full definition →