When Tosfos refer to "Tosfos", who do they mean?

Question

According to Wikipedia, the Tosfos to Moed Qatan were written by a student to a certain Rabbi Yitzhak. Do we know anything about who he was or where he lived?

Specifically, to whom is he referring in Moed Qatan 18b (s.v. אין כותבין) when he contrasts his views with those of "the [other] tosafists"? In other words, when he says "פירשו בתוספות" is he referring to an edited collection called Tosfos (like the one that we have - maybe even the very one that we have) or to the opinions of individual tosafists, which may or may not have been committed to writing?

Answer 1

The Tosafos printed on most of the gemara was written by R' Eliezer of Touqes. It is a summary of the Tosafos of R' Shimshon of Sens (referred to in Tosafos as Rashb"a, R' Shimshon ben Avraham, not to be confused with R' Shlomo ibn Aderes, who lived later.) That Tosafos is based on the teachings of R' Yitzchak of Dampierre, nephew to Rabbeinu Tam and great-grandson to Rashi. (There were other Tosafos like Tosafos HaRosh, Tosafos R' Peretz, etc.) Unless given reason to think otherwise, I would assume the R' Yitzchak referred to is R' Yitzchak of Dampierre. I believe the Wikipedia author means we can't know with 100% certainty, but that is the safe choice.