The much more common expression is to "work under," but I saw "work underneath" in this Wikipedia article and for some reason it bothered me:
In return, the empress worked underneath her and received formal artistic training.
I know that some distinction between under and underneath can just come down to what sounds right to native English speakers as two words are extremely similar (talked about here on this site), but "underneath" does seem to be used more exclusively in a locational sense.
The site idioms.thefreedictionary.com has an entry for "work under" but not "work underneath." The Google tracker also puts the usage of "work underneath" basically always somewhere near zero. Is there a right and wrong answer or can two words be used interchangeably in this expression?