A favourite Yeats poem, for decades. I always figured: if
Augusta Gregory's cat, maybe an anglicised corruption of something Irish, such as
Mien na Loisce, or some equally nonsensical variant. If the cat belonged to one of the Gonnes, most likely French, in which LOUCHE means "disreputable" or "sordid", from the Latin for "cross-eyed"; thus, Little Scoundrel perhaps, or maybe even Little Cross-Eyes, since so much is made of his eyes in the poem.