You are about to be struck during a pillow fight
Turns out to derive from a song (see Notes)
Granny Dixon – 1950s
Marion Dixon (Howes) – mother of Mum, spouse of Pop
Black pudding is a blood sausage associated with northwest England, where Granny & Pop lived for most of their lives.
Oct 2023:
Following a spike of interest in this entry I dug a bit and discovered that it’s from a song reasonably well known in northeast England.
The relevant verse, in one version, runs thus:
All of a sudden a little black pudding
Came flying through the air
It missed my Ma, and hit my Pa
And knocked him off his chair
…which just happens to be the least rude part of the song in every variation I found.
The general consensus on Mudcat seems to be that it should be sung to the tune Blaze Away (by Holzmann but sounds as if it should be by Souza).
—Mark