The Nordwestblock (German, "Northwest Block") is a hypothetical Northwestern European cultural region that some scholars propose as a prehistoric culture in the present-day Netherlands, Belgium, far-northern France, and northwestern Germany, in an area approximately bounded by the Somme, Oise, Meuse and Elbe rivers, possibly extending to the eastern part of what is now England, during the Bronze and Iron Ages from the 3rd to the 1st millennia BCE, up to the onset of historical sources, in the 1st century BCE. The theory was first proposed by two authors working independently: Hans Kuhn and Maurits Gysseling, whose proposal included research indicating that another language may have existed somewhere in between Germanic and Celtic in the Belgian region. The term Nordwestblock itself was coined by Hans Kuhn, who considered the inhabitants of the area neither Germanic nor Celtic and so attributed to the people a distinct ethnicity or culture up to the Iron Age. So far, this has not been proven or disproven. Language hypotheses The hypothetical language or languages spoken by the Iron Age Nordwestblock population are a matter of speculation, as there are no written records of such languages as is the case with the Germanic language, but can be inferred based on analysis of substrate features in the primarily West Germanic languages that later came to be spoken in the region (for example, areal loanwords of unknown origin, and the presence of certain geminate consonants that cannot be explained by inheritance from Proto-Indo-European), or by analysis of place-names (toponymy and hydronymy). Broadly, this substrate area is sometimes called the North-West European substratum. Kuhn speculated on linguistic affinity of this substratum to the Venetic language, while other hypotheses connect the Northwestblock with the Raetic ("Tyrsenian") or generic Indo-European languages of the centum type (Illyrian, "Old European"). Gysseling suspected an intermediate Belgian language between Germanic and Celtic, that might have been affiliated to Italic. According to Luc van Durme, a Belgian linguist, toponymic evidence of a former Celtic presence in the Low Countries is almost completely absent. Kuhn noted that since, in Proto-Indo-European (PIE), the phoneme * was very rare, and since PIE *, via Grimm's law, is the main source of regularly inherited in words in Germanic languages (except after fricatives, e.g. initial *sp- from PIE *(s)p-), the many words in which occurs must have some other language as their source. Similarly, in Celtic, PIE * disappeared and in regularly-inherited