store, accumulate

積 is composed of 禾 (grain) and 責 (duty). 禾 represents grain crops, while the original meaning of 責 is collecting taxes or demanding repayment of debts. In ancient times, taxation mainly consisted of collecting grain, and the grain taken as tax was stored in official warehouses. Therefore, 積 is used to mean to store up or to accumulate, and also carries the sense of piling up or amassing.