One of the hypotheses supported by Theo Vennemann and other linguists is that Proto-Germanic was influenced by some Semitic language. The evidence they present for their case includes:
- Loss of some grammatical cases from Proto-Indo-European. This would be an indication of language contact, with adults trying to learn a different language and simplifying it in the process. This phenomenon has not occured in other languages spoken at the time, such as Latin and Greek.
- One third of Germanic roots do not trace back to PIE, and some of these words seem to have common roots with Semitic languages. For example, Proto-Germanic *furkhtaz, Proto-Semitic *prkh, 'fright'; Proto-Germanic *magaþ, Early Semitic makhat, 'maiden'.
- Grimm’s law, that has introduced the fricative consonants *[f], *[h] and *[θ]. PIE was poor in fricatives, compared to Semitic languages.
- Some deity names also seem to have common origins, such as Old High German Phol and Semitic Baal. These names can also be derived independently through regular sound changes, such as the Grimm’s law.
- Verbs are inflected for tense only in the present and past (like Semitic languages). Other Indo-European languages have a much richer system of verb inflections for marking tense.
- The use of ablaut for marking the past of strong verbs.
Are these observations strong enough to posit a Semitic substrate in Proto-Germanic?