The article discusses the continuation of Proto-Slavic core *grom-// *gram-// *grm- in Polish anthroponymy and topon- anthroponymy and toponymy. Alternation hits them core grom-//gram-, which some researchers combine phonetic processes in the second of them — conformed to the distance of the vowels o under the influence of a further. Problem is just a lack of credentials of assimilation in the Polish language in earlier times. Therefore, the article is an attempt to look for other solutions to this problem.
