Non-grammarians could not provide a hoot, but ELU just isn't directed at them. Not to mention the OP specifically asked regarding the POS of "here" and warrants an answer depending on existing contemplating. The entry then lists dozens of cases of this cluster of terms from 1852 to 1942, and https://dallasufrzg.goabroadblog.com/32876289/the-smart-trick-of-more-info-that-no-one-is-discussing