One way to picture accumulator: something is being added to the same heap, over and over, and nothing is taken off. A of washed jam jars. A number that grows by one more amount each time round the loop. A tank taking in pressure a little at a time. Money left on the table after a win and pushed onto the next result. The word never names the heap itself — it names the one doing the piling, the person, the part, or the place where the pile sits.
From the word’s history
The supplied source traces the word to Latin accumulātor, from the verb accumulō, formed from ad- (to, towards) and cumulus (a heap). Literally, the one that adds to the heap — which is the picture that all five uses still show.
來源資料把這個字追到拉丁文 accumulātor，來自動詞 accumulō，而 accumulō 由 ad-（往…去）加上 cumulus（一堆）組成。字面上就是「往那一堆上面再加的那一個」。上面那幅畫面並不是後來附會的，它在組字的成分裡就寫著了。
Wiktionary, "accumulator"
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