- William => Guillaume
- War => Guerre
- Wasp => Guêpe
- Waffle => Gauffre
All of these 'g's are pronounced as in "gas. "gu" makes the 'g' hard in front of vowels that would have made it soft.
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[1] https://en.wikipedia.org/wiki/Grimm's_law
Of the Grimm Brothers, the same responsible for Grimm's Fairy Tales. Jacob was a philologist in addition to a mythologist.
It's fun because the myth collection was almost a side effect of the linguistics work: it shouldn't be a surprise that when the Brothers Grimm walked into a small village and asked for the oldest documents the village could find they got a lot of interesting myths and fairy tales in return. There's a bit of dramatic irony that Grimm's Fairy Tales has had such a homogenizing force on the myths since its publication when a lot of the reason for collecting them in the first place for the Grimms was seeking all the little nuances and differences and distinctions between them (including and especially linguistically).
If you want to one level deeper, the sound 'F' came to represent is the 'voiceless labiodental fricative'. This means it has a pairing in the pronunciation space with 'V', the 'voiced labiodental fricative'. So Greek 'Digamma' became Latin 'F' in form, which is paired with Latin 'V' which became English 'W' which originally was represented by Greek 'Digamma' in sound.
None of this really means anything, but it tickles my brain.
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[1] Albeit with very different evolutionary paths; English 'w' was used, in part, to allow representation of both Germanic and Latinate words.