One way to hold cruiser is as the thing that cruises. To cruise is to keep moving along at an easy, steady pace, covering an area rather than racing to one fixed point. Add -er and you get the one that does it. A navy cruiser rides far out and stays at sea on its own. A police cruiser rolls up and down the same streets. A pleasure boat and a fat-tyred bike do the same thing for fun. In every case the movement is and the point is the going, not the arriving.
cruiser 可以想成「一個會 cruise 的東西」。cruise 是穩穩地一路前行，在一片範圍裡來回移動，不急著趕到某一個點。再加上 -er，就成了「做這件事的那一個」。海軍的巡洋艦能自己遠航、久留海上；警車在同幾條街上來回巡；遊艇和粗胎單車則是把同一件事拿來玩。四個意思的共同畫面都是：不趕路，過程本身就是重點。
From the word’s history
The word is cruise + -er, literally the one that cruises.
這個字是 cruise 加上 -er 組成的，字面就是「巡行的那一個」。這條線索跟今天的四個意思都對得上。
Wiktionary entry for cruiser, supplied in the evidence packet (source_ref kaikki:3f6f69a190036ae4:849920520): From cruise + -er.
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