The poem's title—"Fog"—is just as short and simple as the poem itself. It doesn't waste any time and makes the most of its contribution to the poem. No need to dress it up with fancy words and obscure terminologies. The poem's about "fog" so might as well use a title that avoids any confusion.
Interestingly, although the title gets right to the point, the "point" is still a mysterious one, since fog is by nature rather unpredictable and a little dangerous. So, even though the title doesn't create any illusions as to what the poem is about, it still sets us up for some imagery and language that serves to capture that elusive movement of fog.