I gave this a little bit of thought and here is my best hypothesis.
The token "yes", which is not a word in Spanish, might have been tried as "Y es".
That in turn being taken as a sentence fragment, meaning "It's a Y". (Spanish isn't verb-final, but let's go with it).
The letter Y is a symbol of forking.
If something is likened to a Y, that's a way of saying it forks.
Anyway, translation tools sometimes do weird things when the input is a sentence fragment or just a word or two.
UPDATE:
When I type "Y es" into Google translate, tagging it as Spanish, those two tokens still go to "Forks". This adds a little bit of support to my hypothesis.
However, "Y e s" also translates to "Forks".
Inputs like "A es", "B es", "C es" don't do anything; they go to "A is", "B is", ...
Moreover "Y es verde" and "Y e s verde" and "Yes verde" all go to "and it's green".
UPDATE:
It is false that "yes" is not a Spanish word. The letter Y is called "ye", and the plural of that is "yes". Just like when we say that giggle has "three gees", we are using a plural of the letter name "gee". https://es.wikipedia.org/wiki/Y