In the northeastern U.S., sometimes also a shivaree/charivari, a mock serenade for a newly married couple using kettles, pans, cowbells, horns, and the like. This word is very much an mid-19th century Americanism, originally specifically a New Year's celebration. The ancestor of the word is Southern British dialect gallithumpians, people who deliberately disturbed Parliamentary elections, of uncertain origin but possibly related to dialect gally, to frighten (as in gallicrow, scarecrow, from Old English agælwan, to scare).
The floats were followed by a large gang of children in a great callithump.
---L.
