“Pickled Stewberries!” in HPMoR, Omake #3

We’re cur­rently trans­lat­ing chap­ter 11 into Ger­man. It’s go­ing along fine, but

“PICKLED STEWBERRIES!”

is still puz­zling us. No dic­tio­nary en­tries, no HPMoR-un­re­lated search hits, noth­ing…

Is this some kind of dadaist joke by Eliezer? Or are we miss­ing some­thing?