Crylo, correct.
The 'husha....' part is similar to that of a Greenaway Mother Goose version from England, c. 1881-
Hush! Hush! Hush! Hush!
We're all tumbled down.

To repeat from posts above, no reports of the rhyme before 1880, and the 'plague' idea is a fanciful interpretation from about the time of the First World War.
See Iona and Peter Opie, 1985, "The Singing Game," Oxford University Press.