You can hold this word as one job title: the one who sends the explosive on its way. Not the one who drives, not the one who plans - the one at the moment of release. Every meaning here is that role somewhere different: in the nose of an aircraft, on the rank list of a gun unit, and, as a joke of naming, on a beetle that back.
bombardier 可以想成一個職稱：負責把爆裂的東西送出去的那個人。不是開車開飛機的人，也不是規劃的人，而是按下去的那一刻在場的人。這一頁的每個意思，都可以當成同一個角色換了地方：飛機的機鼻裡、砲兵的階級表上，還有一隻會反擊的甲蟲身上。
From the word’s history
The evidence packet derives the word from bombard plus -ier, by way of Italian bombardiere and Middle French bombardier - literally the person who works the bombard, an early cannon.
提供的來源把這個字拆成 bombard 加 -ier，並經由義大利文 bombardiere 和中古法文進入英文。字面就是「操作 bombard（早期火砲）的人」。
Wiktionary, "bombardier"
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