What does 土 mean in this sentence 这个名字有点土?
土 has serveral meanings, one of which is 不合潮流 (out of the swim, out of fashion, out of step, old-fashioned, etc.). 

So in your example, 土 means old-fashioned.

I guess it is because the core meaning of 土 is earth or dirt, which we can't say is fancy.