Think of lying very still in a patch of warmth and letting it soak into you: a cat on a doorstep, a lizard on a hot stone, you on a bench in the winter sun with your eyes half shut. Nothing is being done and nowhere is being gone. The warmth arrives, the body stays, and the whole point is that it feels good. Everything bask does keeps those three parts — a source of warmth, someone sitting in it, and the enjoying.
From the word’s history
Wiktionary traces bask to Middle English basken, from Old Norse baðask, literally to bathe oneself, and calls it a doublet of bathe. Bathing yourself is exactly the core picture: you get into the warmth all over and stay there.
Wiktionary 把 bask 追到中古英語 basken，再上溯到古北歐語 baðask，字面是「幫自己洗澡」，並說它和 bathe 是同源雙式詞。這正好就是核心畫面：整個人進到溫暖裡，然後待著不動。
Wiktionary entry for bask, kaikki extract kaikki:3f6f69a190036ae4:963917701:16297 (Middle English basken < Old Norse baðask, doublet of bathe)
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