A while back I was talking to someone who was delivering a talk on security when an odd thing happened. Whenever he was talking about phishing, he kept calling it "fizzing". I spoke to him afterwards, apparently he had no idea what the significance of the "ph" in phishing is. All you old time hackers should already know this so move along, nothing to see here! But for everyone else: back when most folks didn't know what computer security was and kids were breaking into everything that had a dial tone & a modem handshake; there developed a culture of "phone phreaks" (pronounced "freaks"). Phreaking was the art and science of bending the phone system and related hardware to your will; usually this had a lot to do with hacking corporate pbx's, calling card numbers, or the actual phone system switches. Other times it was just playing around with things you found while calling random numbers, like the default passwords for cellular voicemail boxes, strange tones and screwy caller IDs. Phreaks also developed the various tone boxes. This was generally a sub-culture however, and most Americans had no idea what was going on or what level of access some of these guys were able to get. For example, this Esquire article from 1971 was really the first time anyone had heard about blueboxes and the cool things you could do with them. (By the way, most if not all of these no longer work :)
Anyway, so the "ph" comes from phone, and that's how phreaking and much later, phishing got it too. It's pronounced like a "F".