words did not reappear in p-Celtic languages except as a result of Proto-Celtic *kʷ becoming *p. All that taken together means that any word starting with a /p/ in a Germanic language that is not evidently borrowed from either Latin or a p-Celtic language, such as Gaulish, must be a loan from another language. Kuhn ascribes those words to the Nordwestblock language. Linguist Peter Schrijver assumes the pre-existence of pre-Indo-European languages linked to the archeological Linear Pottery culture and to a family of languages featuring complex verbs, of which the Northwest Caucasian languages might have been the sole survivors. Although assumed to have left traces within all other Indo-European languages as well, the influence of an unknown substrate would have been especially strong on Celtic languages originating north of the Alps and on the region including Belgium and the Rhineland. It is uncertain when Germanic began to gain a foothold in the area. The Nordwestblock region north of the Rhine is traditionally conceived as belonging to the realms of the Northern Bronze Age, with the Harpstedt Iron Age generally assumed to represent the Germanic precedents west of the Jastorf culture. The general development converged with the emergence of Germanic within other previously Northern Bronze Age regions to the east, maybe also involving a certain degree of Germanic cultural diffusion. From about the 1st century CE, that region saw the development of the "Weser-Rhine" group of West Germanic dialects which gave rise to Old Frankish from the 4th century. The issue still remains unresolved and so far no conclusive evidence has been forwarded to support any alternative. Mallory considers the issue a salutary reminder that some anonymous linguistic groups that do not fully obey the current classification may have survived to the beginning of historical records. Prehistoric composition The archaeological case for the Nordwestgroup hypothesis refers to a time as early as 3000 BCE. The following prehistoric cultures have been attributed to the region and are compatible with but do not necessarily prove the Nordwestblock hypothesis. The Bell Beaker culture (2700–2100 BCE) is thought to originate from the same geographic area, as early stages of the culture apparently derived from early Corded Ware culture elements, with the Netherlands/Rhineland region as probably the most widely accepted site of origin (J. P. Mallory, EIEC p. 53). The Bell Beaker culture locally developed into the Bronze Age Barbed Wire Beaker culture (2100–1800 BCE). In