One way to hold propel is a force sitting behind something and sending it forward. The force is not a single tap; it works on the thing and the thing travels. Put a motor behind a boat and the boat crosses the water. Put a hand on a person's back and the person goes through the door. Put one lucky event behind someone's life and they end up somewhere they were not before. The thing being moved changes from a hull to a body to a whole situation, but the picture stays the same: power at the back, movement at the front.
From the word’s history
Latin propello is pro- forward plus pello to push, so the word literally means to push forward.
拉丁文 propellō 由 pro-（向前）和 pellere（推）組成，字面就是「往前推」。這個組合跟今天三個用法的畫面完全一致。
Wiktionary entry for propel, supplied in the evidence packet (source_ref kaikki:3f6f69a190036ae4:677737255): From Middle English propellen, from Latin propello, from pro- (forward) and pello (to push, to move).
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