Matt Koegler was credited by Frank Zappa for coining the phrase 'Mothers of Prevention' on the 1985 release 'Frank Zappa Meets the Mother's of Prevention'.
I asked Matt how and when the title came about, and how he told FZ about it. Here's his answer:
"The title really sort of just came out of my mouth. By coincidence, I was sick on the day of the Senate hearings and stayed home from work. The entire thing was broadcast on C-Span that day and since Frank was testifying, I decided to watch and record it. That night when everyone came over for rehearsal (I lived in the Band House) we watched it. At some point, Frank used the phrase 'Washington Wives' in his testimony and I said "Yeah, the Mothers of Prevention" and we got a good laugh. A few weeks later I wrote to Frank requesting a Z-Pac (info on the ratings issue, still have it somewhere) and I opened the letter with "Dear Mr. Zappa: First, thanks very much for standing up to The Mothers of Prevention.". Frank apparently thought it was funny and used it as the next album title. I received no notice of this, I discovered it while standing in line and reading the credits on the back of the album (this was the last vinyl release of new material before all new releases came out on CD). I called 818 PUMPKIN and thanked them, Frank wasn't in the office at the time, but they said a thank you to me on that weeks answering machine recording (I still have that as well).
I was supposed to meet him at the show in New Orleans, Louisiana during the 1988 tour, but that was to be on the 3rd leg of the tour which never happened. I never bothered him about it again, just continued to purchase the music and turn others on to it."