"Remember"—that's it. Pretty simple title, right? Yep, it's just one word that summarizes the poem's major theme: remembrance. This is a poem, after all, spoken by a woman who is thinking about her death and wants to make darn sure that her beloved never forgets her. Okay, actually she's obsessed with making sure her beloved doesn't forget her. It's almost like she's worried that he might do exactly that. Hmm, well that's not a very pleasant thought now is it?
This brings us to another important idea about this poem's title. It is a command, an order—an imperative. The title might as well be "Listen you, remember me or else!" Sure, it's not quite that bossy, but the speaker definitely orders this guy to remember her at least four times, if you include the title. The fact that an imperative introduces the poem, and that keeps popping up, confirms what we've already noted: the speaker is worried that her beloved will forget her, and is overcompensating.
Sure, by the end of the poem the speaker basically changes her mind, and says, essentially, "On second thought, it's better that you forget me because remembering me might cause too much pain, and I just can't have that," but for most of the poem, she's more concerned with making sure he doesn't forget her. When you, ahem, remember this, it kind of makes the title seem a little deceptive, doesn't it?