The Japanese word for the fruit is also borrowed from English, resulting in the much closer レモン remon. But the spelling is borrowed from Chinese (when kanji are used at all), despite the pronunciation coming from elsewhere.

> There are kanji less obscure than 論. There are some that are so common that even I know them. It is in the 6th grade jōyō kanji, but I doubt it's in the top 1000 most common characters in Japanese, maybe not even the top 2000. You could probably guess that 侖 is the phonetic

It's not an especially common character in Chinese either, though it is part of some common words like 讨论. (论 is the simplified form of 論.) But frequency of occurrence isn't the only way you can fail to be obscure. I call this one of the least obscure characters in existence because it is the name of the most prominent Confucian work, the one conventionally titled Analects in English, 論語 "discussions".

Consider that "spangled" is not a word in common use in the USA, but Americans can be expected to recognize it anyway.

> Did anyone guess "rin"?

I don't remember.

> Presumably when prewett said "When the Japanese imported it, they used the characters much more phonetically," they meant onyomi. (Perhaps they didn't know about kunyomi.) When they say, "but the characters got assigned to the Japanese pronunciation of the word," that is mostly wrong as a description of how Japanese writing uses kanji today

I read prewett very differently than you do. To me, when he says "the characters got assigned to the Japanese pronunciation of the word", he is referring to kunyomi. I don't think that's wrong as a description of how Japanese writing uses kanji today. But I do think it's wrong to describe that use as "much more phonetic" than the Chinese writing system. I see it as much less phonetic.