There has been a question that I have been wondering about for a while. Peter先生 has mentioned it often, and ruminated on the origin of a certain Japanese word, and after my Chinese lesson today, I think that I have the answer.
赵高 was a courtier in ancient China. One day, in order to demonstrate his power to the emperor (who he wanted to overthrow) he brought a deer to the imperial court. He told all of the other courtiers that the animal was a horse. 赵高 was such a nefarious bastard that no one was brave enough to contradict him. He was trying to make a point to the emperor, that everyone was so afraid of him that they wouldn't dare contradict him on such a simple issue.
From this story, we get the Chinese idiom "指鹿为马", or "to point at a deer and call it a horse". When someone is deliberately changing or obscuring the facts for to their own ends, they are said to be "pointing at a deer and calling it a horse".
Is this the origin of the Japanese saying "馬鹿"? There can't be many other idioms that involve horses and deer, and although the meaning of 指鹿为马 isn't quite the same as 馬鹿 I think that the Japanese saying has come from the Chinese idiom.
actually, i remember that lesson well.
but the stories of confusing deer and horses, etc., smacks of folk etymology to me. i'd be very interested in hearing a japanese etymologist's opinion on the matter.
i heard from a friend (not an etymologist) that this is a case of 当て字.
as you well know, there are many words in japanese that precede the importation of kanji. (of course there are also words imported from china and also those created later). バカ is a very old word of unknown origin. one theory is it's japanese and pre-dates kanji. another is that it came from chinese (but not necessarily with those characters).
i just checked gogen, and it says the word comes from sanskrit "baka" or "moha" and that the chinese wrote this word as 莫迦 (bakuka）and 募何 (boka). apparently those spellings didn't fly so well with the japanese who applied the 当て字 「馬鹿」.
both of those explanations are pretty close. and not as far fetched as the more colorful (but unlikely) stories.
for those who aren't familiar with the term, 当て字 refers to kanji used for their sound values, not ideographic meaning.
寿司、亜米利加、珈琲、煙草、基督 are other examples of 当て字.