Definitely a palm, no idea which until it develops adult foliage.

Same thing happens here. Yes, a palm...I think birds drop the seeds. Sorry I don't know what kind. I pull them before I can find out.

I get them in my yard too. I let one grow, and it turned out to be Phoenix roebelenii, pygmy date. (My neighbors a few doors down have one.) I'll bet if you scout around your neighborhood, you will find the mama tree.