I think this is a hangover from the iStock's
great leap forward of a year and a bit ago. (Boy! And what an improvement! It was so amazingly cool you could see your breath on site.

)
At that time, without warning anybody, they suddenly changed their whole keywording system into one using 'tags' instead of the keywords that the owner of any picture had entered.
And, to get over the problem of all the existing images that had already been carefully (?) keyworded by the author, they set up an automated system to change those keywords into their new 'tags'.
I'm not sure how intelligent the programmers who set up that circus were, but it gave rise to some bizarre results.
I suffered along with many others. Several of my images ... a picture of a house ... three or four pictures of an older model I was using ... and some pictures of fruit ... all suddenly acquired the keyword 'anus'.
We poor photogs were supposed to sort out the resulting mess by 'disambiguating' our images. Some of us are still doing it. (And isn't it fun.)
I would guess the owners of the photographs that come up in this search haven't got around to disambiguating them yet.