Picture something that one hand cannot manage — a full tray, a heavy sword, a ball coming in fast. A second hand has to come and join the first. That is the whole picture: not one, but two. English then does something quiet and useful with the word hand: it lets it stand for a person, as in all hands on deck or a hand at cards. Once hand can mean a person, counting to two counts people instead of fingers, and the same word can describe a saw that needs two workers.
可以想成一件一隻手應付不來的事：端滿滿一盤菜、握一把很重的劍、接一顆飛過來的球。第二隻手就得過來幫忙。畫面就是這樣——不是一隻，是兩隻。英文接著在 hand 上悄悄做了一件很好用的事：讓它也可以代表「一個人」，像 all hands on deck（全員上甲板）、a hand at cards（牌桌上的一個人）。一旦 hand 可以指人，數到二就變成在數人，同一個字也就能拿來形容一把要兩個工人一起拉的鋸子。
From the word’s history
The source entry records the word simply as two + handed, which matches the picture directly: 'to do with two hands'.
資料來源把這個字記成 two 加 handed，字面就是「跟兩隻手有關」，正好對上這個畫面。後面的分岔，只看 hand 被讀成手還是被讀成人。
Wiktionary, "two-handed"
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