Picture someone out and calling: who are you, and what are you doing here? That call is the challenge. Unchallenged is the word for what happens when it never comes. Nobody steps out, nothing is asked, and whatever was walking past just keeps walking.
可以想成這樣一個畫面：有人從旁邊站出來，喊一聲——你是誰？你要做什麼？那一聲就是 challenge。unchallenged 說的是那一聲沒有響。沒有人站出來，沒有人問，剛剛經過的東西就這樣繼續走下去。走過去的可能是一個人，也可能是一句話、一個第一名的位子，或是一整年都太簡單的功課。
From the word’s history
The packet gives the word as un- plus challenged, with un- coming down through Old English from a very old negative element. So the word is built, not borrowed: take the act of challenging and cross it out.
來源把這個字拆成 un-（不）加 challenged，而 un- 這個否定的成分一路從古英語往上追得很遠。所以它是拼出來的，不是借來的：把「挑戰、喝問」這個動作畫掉，剩下的就是這個字。
Wiktionary etymology tree supplied in the evidence packet (source_ref kaikki:3f6f69a190036ae4:872410615): un- + challenged.
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