One way to picture it: something standing up that a single finger can knock flat. The whole word lives in that one moment — no effort, and it is over. Push a person and you get someone who gives in; push a task and you get something you finish without trying. English leans hardest on the negative: no pushover means it does not go over.
From the word’s history
The packet gives pushover as a deverbal from the phrasal verb push over, first appearing around 1891. The noun simply freezes the action of the verb into a thing or a person.
字源資料說 pushover 直接從動詞片語 push over（推倒）變成名詞，大約 1891 年出現。名詞等於把「推倒」那個動作凍結成一個人或一件事，所以畫面才留得這麼清楚。
Wiktionary entry supplied in this packet (source_ref kaikki:3f6f69a190036ae4:732882883): 'A deverbal from push over. First use appears c. 1891 in the Galveston Daily News.'
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