Stella
If you're ever given an exam where you are required to identity the author of a poem, with no information other than the poem itself, and that poem contains the name "Stella," there's a 99.9999% chance that it's Sidney (just like if you get a poem about Lucy it's usually Wordsworth; if about Julia, it's Herrick; and so on). Sure, other poets have probably used the name Stella (though we can't think of one off hand, and we know everything), but it's not a distinguishing feature of anybody's poetry but Sidney's. The sonnet sequence from which "Come Sleep! O Sleep" is taken is called Astrophel and Stella, after all, and the name "Stella" is everywhere. Everywhere, Shmoopers. Just take a quick glance at Sonnets 5-13 to see what we mean.