(quoted in full from The Goldberg Variations website)
"On Aug 5, 1705, Bach appeared before the Consistory to complain about the student, Geyersbach. The latter - as Bach was crossing the market place on his way home from the Castle with his cousin Barbara Catharina, daughter of Johann Christoph Bach, Court and Town Musician in Arnstadt - had been sitting on the "Long Stone" with five other students, and had suddenly set upon him with a stick, calling him to account for having made abusive remarks about him.
"Bach had answered that he had not made abusive remarks about him, and no one could prove that he had, seeing that he had been going his way perfectly quietly. But Geyersbach had replied that if Bach had not abused him, he had once abused his bassoon, and whoever abused his things abused him; that Bach was a dirty dog (Hundsfott); and with this he had at once struck out at him. Bach, for his part, had thereupon drawn his sword, whereupon Geyersbach had fallen into his arms, and the two of them had tumbled about until the other students had thrown themselves between them.
"On Aug 29, at a further hearing, it developed that Bach had indeed called Geyersbach a nanny-goat bassoonist (Zippelfagottist), and it was indicated to him that he might well have refrained from this - especially as he already had the reputation of not getting along with the students and of claiming that he was engaged only for the simple chorale music, and not for concerted pieces, which was wrong, for he must help out in all music-making.
"Bach answered that he would not refuse if only there were a Director musices, whereupon he was told that man must live among imperfecta, that he must get along with the students, and that they must not make each other's lives miserable."
-Weissgerber, "Johann Sebastian Bach in Arnstadt, 1904," as quoted in The Bach Reader (David and Mendel, The Norton Library, 1965).
More "unconventional quotes" relating to Bach are here. I've also added that site, which is yet another good online resource on Bach and his music, to this blog's list of music and piano sites.
And the next time you want to gravely insult your friendly neighborhood bassonist, I'm sure that calling him/her "Zippelfagottist!" would do the job quite nicely.