My wife is trying to learn German and I'm trying to relearn it, so I help her when I can...
This evening she calls out to me from another room: "How do you pronounce a 'W' in German?"
Me: "It's pronounced like a 'V'."
Her: "So, how do you pronounce a 'V' in German?"
Me: "It's pronounced like an 'F'."
Her: "Okay, so how do you pronounce an 'F' in German?"
Me: "It's also an 'F'."
Her: "Any reason why?"
Me: "Perhaps in the distant past they were pronounced just like we do in English. It probably changed over time when they all started speaking with German accents."