真的用劍的人
這是字面直接長出來的一支：劍就是劍，本事就是劍術。
noun · B2
A man who is good at fighting with a sword, either in a real fight, in the sport of fencing, or in a story or film.
劍客；劍術高手
核心畫面
One way to hold swordsman: a man with a blade in his hand, and the word is not pointing at the blade. It is pointing at what he can do with it. Anyone can carry a sword; a swordsman is the one who has the skill, and the word carries a little admiration for that skill wherever it goes.
可以想成這個畫面：一個男人手上握著一把劍——而這個字指的不是那把劍，是他用劍的本事。誰都可以拿著劍，但 swords…更多收起
可以想成這個畫面：一個男人手上握著一把劍——而這個字指的不是那把劍，是他用劍的本事。誰都可以拿著劍，但 swordsman 是那個真的會用的人。這份「有本事」的味道，不管這個字走到哪個用法裡都還留著，只是被用在什麼事情上會變。From the word’s history
From sword + -s- + man.
來源可以想成 sword（劍）＋ -s- ＋ man（人），字面就是「用劍的人」。中間那個 -s- 跟 sportsman、craftsman 是同一個接縫。
Wiktionary entry for swordsman (kaikki extract, source_ref kaikki:3f6f69a190036ae4:1286981394): "From sword + -s- + man."
Two branches
俚語：把劍當成身體的比喻
核心畫面裡的「劍」被當成男性身體的比喻，於是「劍術好」整個換了對象，變成在講性經驗。這是比喻的延伸，不是另一個來源。
noun · C1
An informal word for a man who has sex with a lot of different women. It is usually said about a man's reputation, in gossip or in the press, rather than about anything anyone has seen.
情場老手（俚語）