從那邊來的男人
這一支就是字面本身：某個地方來的男人。範圍隨著時代收窄，從「講日耳曼語的人」縮到「荷蘭人」。
noun · B1
A man from the Netherlands.
荷蘭男人
核心畫面
Start with the plainest reading: Dutch plus man, a man from the Netherlands. Around that sit uses that have drifted away from it — an older, wider Dutch that also covered German speakers, and a spoken formula where being a Dutchman simply stands for something impossible. A separate workshop word, written with a small d, has travelled of all.
先從最直白的讀法開始：Dutch ＋ man，一個從荷蘭來的男人。其他用法圍著它，但都已經走遠了一點——舊英文裡的 …更多收起
先從最直白的讀法開始：Dutch ＋ man，一個從荷蘭來的男人。其他用法圍著它，但都已經走遠了一點——舊英文裡的 Dutch 範圍更大，連講德語的人也罩進去；口語裡還有一個固定句型，把「我是荷蘭人」當成一件不可能的事來用。另外有一個工坊裡的字，寫成小寫 dutchman，走得最遠。From the word’s history
From Middle English Ducheman, that is Dutch plus man. The root behind Dutch (Middle Dutch duutsch, Middle Low German dutsch) is the same one behind German deutsch, which is why older English could use Dutchman for a German.
來自中古英語 Ducheman，也就是 Dutch ＋ man。Dutch 背後的字根（中古荷蘭文 duutsch、中古低地德文 dütsch）跟德文 deutsch 同源——這條共同的根，正好解釋了為什麼舊英文可以用 Dutchman 指德國人。
Wiktionary entry Dutchman, etymology tree supplied in packet (source_ref kaikki:3f6f69a190036ae4:274015382:35013)
Two branches
拿「我是荷蘭人」當作不可能
這一支借的不是「荷蘭人」的內容，而是「說話的人顯然不是荷蘭人」這個事實。
noun · C1
Used in the fixed phrase if ..., then I'm a Dutchman, to say you do not believe what has just been said. You claim something impossible about yourself to show the other thing is just as impossible.
才怪；我才不信