One day a math student in Britain was writing out an identity matrix while trying to solve some linear algebra problem, and was so struck by the notational shorthand of the Kronecker Delta that he decided to attempt to immortalize its creator in the minds of British college students for all eternity by doing the most obvious and common thing: brewing his own German lager and naming it Kronecker Delta.

Certainly, he thought, that if he named a beer after Kronecker's brainchild, it would one day be of use during some student's physics final, like when he'd come across a matrix manipulation problem, forget the format of the identity matrix, let his mind drift to last weekend when he got drunk on the roof of one of the science buildings, and remember the fine German lager he was enjoying that night: Kronecker Delta.

Okay, so I totally made that entire story up, but that's definitely the only possible way this could have been invented.