Picture a ship lying beside you: not the narrow bow, not the stern, but the long flat face in between — the broadest side it has. Broad plus side says exactly that. Everything else in the word can be seen growing out of that face: the row of guns set along it, the roar when the whole row at once, the burst of criticism that lands the same way, and the plain idea of being turned, or hit, on the long side instead of the front.
From the word’s history
The packet's Wiktionary entry gives only the make-up of the word: 'From broad + side.' It does not trace how each later use appeared. So the links drawn above are offered as a way of holding the word together, not as a history of it.
手上的 Wiktionary 資料只寫了這個字的組成：broad + side。它沒有交代後來各個用法是怎麼一步步出現的。所以上面畫的那些連結，是幫助你把這個字握在一起的線索，不是歷史考證。
Wiktionary, "broadside"
登入就可以看每一支怎麼連回核心畫面。