Gausus[31] The common religious vocabulary between Celtic and Germanic languages suggests that speakers of Proto-Germanic and Proto-Celtic were in close contact in ancient times and likely shared some of their beliefs.
[215] Historian John T. Koch argues that Pre-Germanic and Pre-Celtic languages remained in close contact from 1800 to between 1200 and 900 BCE, partly due to the long-distance metal trade with Scandinavia.
A few of these terms can be identified as Celtic loanwords that entered the Germanic languages between 900 and 500 BCE, after the sound changes in Proto-Celtic had been completed.
[217][218] Edgar Polomé writes that the "acceptable lexical evidence exclusively shared by the Germanic, Baltic, and Slavic tribes is hardly sufficient to draw any definite conclusions as to their close relationship".
For instance, the Proto-Germanic word for werewolf (*wira-wulfaz, 'man-wolf') appears to be semantically related to the Proto-Slavic and Proto-Celtic equivalents *vьlko-dlakь ('wolf-haired') and *wiro-kū ('man-dog'), respectively.