Rabbenu Peter?

(Gittin 8a) "...תוס' ד"ה רבי יהודה אומר: שאל רבינו פטר לר"ת"
"Rabbenu Peter (?) asked Rabbenu Tam..."

In four or five places in the tosafos on Shas a Tosafist called רבינו פטר is quoted. Usually פטר is vocalized "Peter," for it is assumed that was his name. While non-Hebrew names are certainly not unusual for rabbis and regular Jews of every era, we don't often find rabbis that share a name with an apostle, certainly not in medieval Europe.

This רבינו פטר was in fact named פטר בן יוסף and was a talmid of Rashbam and Rabbenu Tam. He was also rabbi in Kaernten in Austria and died there in 1146 during the 2nd Crusade.

The name seems strange, even allowing that in Talmud Yerushalmi a R. Yose ben Pitros is mentioned--sometimes that name is given as פרטא, פטרון, or פנחס. In short, there is room to doubt that R. Yose's father's name was some variant of Peter, but even if it was the possibility of copy errors here suggest that the name was very strange. And we've still got to explain why a baal ha-tosafos was named Peter. The relationship with Christians was certainly of an entirely different dynamic in the time and place of the Tosafists. There is otherwise no example of a Jew named Peter in the Middle Ages. In fact, this name would seem quite verboten, if you consider how R. Yehuda Ha-hassid quoted the name in Sefer Hassidim:

"כמו שמעון כיפה שאומרים פטר חמור"

According to H.J. Zimmels (JQR Vol. 48, No. 1. (Jul., 1957), pp. 51-52.) this is all one big mistake. The name פטר should be vocalized "Pater," the common translation of the name "Abba." In the Middle Ages Hebrew names were often translated into Latin (e.g., Justis for Zaddok, Vivacius for Hayyim). If so, perhaps Rabbenu Peter ben Yoseph was actually named Abba (at least at his bris!), and he was really Rabbenu Pater.