Green’s Dictionary of Slang

to hit a hard surface, with a slapping or splashing noise; thus splattering n., a beating.

1922		J.A Dunn Man Trap 226: A bullet whistled by Jimmy’s head, splatting on the lava crust.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 401: The miscreant receives what is variously termed a bashing, [...] slapping, splattering.
1977		S. Berkoff East in Decadence and Other Plays (1985) 49: The sheet of red that splat from out his pipes did dull it.