Just for the sake of commpleteness -

There's also the practice that the first line is characeristically (there's a nice one for you) two nonsense words, paradigmatically (there's another) "Higgledy Piggledy" but anything will do.

Hoggamus Higgamus is another, and has an interesting history (as in Hoggamus Higgamus/Men are polygamous/Higgamus Hoggamus/Women monogamous").

The Irish Washerwoman also has the dubious distinction of fitting exactly the chemical "Paradichloroaminobenzaldehlyde" (a quadruple-dactyl, no less) repeated four or eight times, including the pickups to the next verse.