In fact, the pattern you noted is so distinctive of Germanic that linguists have actually given it a name: https://en.wikipedia.org/wiki/Grimm%27s_law#Examples

In fact, the pattern you noted is so distinctive of Germanic that linguists have actually given it a name: https://en.wikipedia.org/wiki/Grimm%27s_law#Examples https://en.wikipedia.org/wiki/Grimm%27s_law#Examples The first part of the law is a general stop to fricative pattern, so not just p->f, but also t->th, k->h, etc.