There are many words in Germanic languages whose roots are difficult to identify. Some believe that the lack of clear cognates among other Indo-European languages is indicative of a mixed origin for the Germanic languages.
One group of these words has to do with ships and the sea; words like keel, oar, rudder, and steer are shared by almost every Germanic language (or at least by the Scandinavian ones), but
cognates for these specific words and senses are not found in other branches of Indo-European. This likely reflects the land-locked nature of the Indo-European homeland. Another group of these words deals with war and weapons; words like sword, shield, helm, and bow are all found in almost every Germanic language, but again, not with these meanings among other ndo-European languages (knight is in this class as well, but does not usually have a military meaning).
The other word senses that occur in this group are names of animals, parts of the body and objects in nature.
While many of these words have been contested as having plausible Indo-European etymologies, others simply do not fit into the sound system of reconstructed Proto-Germanic. For example, those words with initial p-, since Proto-Germanic lacked this sound.
Some of these words are shared with a few other Indo-European languages found or originating in Northern Europe. There have been four major theories to account for this linguistic borrowing:
Theo Vennemann suggests that the loans in Northern European and Greek come from an Afro-Asiatic language he calls Atlantic, and from Vasconic, the ancestor of the modern Basque language.
Hans Krahe uses the term "Old European" to identify the source of ancient European river names.
Hans Kuhn identifies a Nordwestblock language from Northwest European placenames and from words in Celtic, Italic and Germanic which violate Indo-European root rules. He also uses the term "Old European," or the ar-/ur- language for a wider substratum source.
Peter Schrijver refers to a "language of geminates" in words from Celtic, Italic, Germanic and Finnic with roots of a certain form. A language of bird names is also associated with this substrate.
Torsten Pedersen has given a new theory that these influences may come instead, at least partly, from an Austronesian source. Again, he sees many of the words involved as related to the "waterfront" including words for fish hooks, fishing poles, bailers and the like.
Some researchers have referred to the substrate language as Folkish under the presumption that the word "folk" is also one of the borrowed words.
Paul Kekai Manansala