Looking at the regular Google search page, it looks like it's getting the answer from here: https://en.wikipedia.org/wiki/Wikipedia:How_many_legs_does_a_horse_h

Looking at the regular Google search page, it looks like it's getting the answer from here: https://en.wikipedia.org/wiki/Wikipedia:How_many_legs_does_a_horse_have%3F https://en.wikipedia.org/wiki/Wikipedia:How_many_legs_does_a..., which is using it as an example of incorrect information without evidence.