One way to hold this word: a spear is a long pole that does nothing on its own, plus one small hard point at the end that does everything. The point touches first, opens the way, and the whole length follows through the hole it made. Every other use is that point, moved somewhere else. A group at the front of a movement is the point. A person who gets a stuck project moving is the point, in verb form.
From the word’s history
From Middle English spere-hed, equivalent to spear plus head. Head here means the front end of a thing, as in the head of a line, not a person's head.
來自中古英文 spere-hed，等於 spear（矛）加 head（頭）。這裡的 head 不是人的頭，而是「一樣東西的最前端」，跟 the head of the line（隊伍最前面）是同一個用法。
packet evidence: Wiktionary etymology_text for spearhead (From Middle English spere-hed; equivalent to spear + head)
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