Etymology of とんでもない


Where did `とんでもない` (meaning "not at all" or "outrageous!") come from?

Could it be `飛んでもない`? ("will not even jump/fly" in a similar way how "When
pigs fly" is considered a remark for something outrageous?)

Or is there a more complete sentence from which `とんでもない` was taken out?




Rough extraction/translation from <http://gogen-
allguide.com/to/tondemonai.html>:

Originally from 途{と}でもない, 途{と} meaning "way", "road", "path". Combined with
adjective 無{な}い, this becomes 途{と}でもない "off the path".




It has nothing to do with flying. Tondemonai derives from an older todemonai.
Some speculate that the initial to is to be identified as 途 (to, "road").
While you may want to further break it into to demo nai, there is little
evidence to support this so you should treat it as a single word. That being
said, modern re-analysis of the final nai into a separate morpheme is quite
common resulting in tondemo arimasen, a supposedly more polite form.

