Think of a dove sitting on a wire, seen from behind. Its tail is narrow where it leaves the body and spreads out wide at the end. Now cut a piece of wood into that shape and push it into a hole of the same shape. Because it grows wider as it goes in, it cannot slide back out the way it came. Everything the word does grows from that one fact: two shapes made for each other, and a hold that needs no nails.
The noun is dove plus tail: the joint is named after the shape of a dove's tail. The verb was formed from the noun afterwards.
名詞就是 dove（鴿子）加 tail（尾巴），直接用形狀命名。動詞是後來從名詞長出來的，所以先有那個榫，才有「把木頭榫起來」這個動作，再往後才有抽象的「剛好吻合」。
Wiktionary entries for dovetail (noun and verb), packet source_refs kaikki:3f6f69a190036ae4:1247590904 and :1247631168 — 「The noun is derived from dove + tail. The verb is derived from the noun.」
Two branches
木工：切成鴿尾形的榫，和榫接這個動作
這一族就是核心畫面本身：真的木頭、真的形狀、真的拔不開。
noun · C1
A joint used in woodwork. Wedge shapes are cut into the end of one board and matching spaces into the other, so that when the two are pushed together they lock and cannot be pulled apart. The word is also used for one of those wedge-shaped pieces on its own.
燕尾榫
抽象：互補到剛好接得上
把木頭換成計畫、時間或想法，形狀互補這件事整個搬過去，連「湊上就牢」的語氣也一起帶走。
verb · C1
If two things dovetail, they fit together so neatly that they work as one; you can also dovetail two plans, jobs or ideas, which means arranging them so that they fit together like that.
吻合