Think of someone who has taken one enormous breath and simply will not stop: the sentence keeps going, the point is somewhere ahead, and the listener has already given up waiting for it. The complaint is never length by itself — it is length that buys nothing. Hold that, and the second use follows without effort: a process can take an enormous breath too.
可以想成一個人吸了一大口氣，然後一路講下去都不停：句子還在長，重點還在前面，聽的人已經放棄等了。抱怨的從來不是「長」本身。抱怨的是這個長度什麼也沒換到。抓住這一點，第二個用法就自己長出來了：一套流程也可以這樣一口氣拖下去。
From the word’s history
From long + winded; wind in this family is breath, so the literal picture is having a long breath.
來源說它是 long 加 winded。wind 在這一族裡可以想成「氣息」，所以字面畫面就是「一口氣很長」。這個畫面跟今天的意思幾乎重疊：話拖著不停，聽的人先撐不住。
Wiktionary etymology supplied in packet: 'From long + winded.' (source_ref kaikki:3f6f69a190036ae4:477839977)
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