1) MAROR THAT HAS A "SHEM LEVAI"
QUESTION: Rav Chisda in the name of Ravina bar Shila rules that one may use "Maror d'Agma" to fulfill the Mitzvah to eat Maror on Pesach night. The Gemara questions this ruling from a Beraisa which states that one does not fulfill the Mitzvah with Maror that has a "Shem Levai" -- a modifying name, "such-and-such Maror." Only generic "Maror" may be used for the Mitzvah, for that is what is mentioned in the Torah.
Abaye answers that since "Maror d'Agma" was known merely as "Maror" at the time the Torah was given, it falls into the category of "Maror" mentioned in the Torah.
Rava answers that "Maror d'Agma" has no modifying name. Rather, "d'Agma" merely refers to the place in which the Maror can be found -- in the swamps ("Agma").
The Gemara here clearly maintains that a type of Maror that has a modifying name may not be used for the Mitzvah of Maror. However, the Gemara in Pesachim (39a) contradicts this ruling. The Mishnah there states, "These are the vegetables with which a person fulfills his obligation [to eat Maror] on Pesach: Chazeres, Tamcha, Charchavina, Ulshin, and Maror." The Gemara cites the opinion of Acherim that "every bitter vegetable [with which one may fulfill the Mitzvah of Maror] emits a milk-like sap when cut, and the vegetable's color is whitish." Rav Huna says that the Halachah follows the opinion of Acherim.
The Gemara there implies that any bitter vegetable (which meets the criteria of having a milk-like sap when cut, and a pale color) is acceptable for use for the Mitzvah of Maror. RASHI on the Chumash (Shemos 12:8) indeed states that the word "Maror" in the Torah refers to "any bitter vegetable."
If one may use any bitter vegetable, it should make no difference what the Maror is called. Why does the Gemara here conclude that the Maror must not have a modifying name? (MAGEN AVRAHAM OC 473:15, REBBI AKIVA EIGER)
(a) The ME'IRI explains that the Gemara in Pesachim (39a) clearly sets forth an order of preference for what type of Maror one should use on Pesach. Chazeres is the first choice, either because it is the most bitter, or because its name alludes to the mercy ("Chasa") that Hash-m showered upon the Jewish people when He took us out of Egypt. The Gemara here does not mean that one does not fulfill his obligation at all with Maror that has a "Shem Levai." Rather, it means that Chazeres with a "Shem Levai" is not considered to be the choice type of Maror. (RASHI, DH Merarisa, indeed explains that the Gemara here refers to a particular type of Chazeres. Tosfos questions Rashi's basis for explaining that the Gemara refers to a type of Chazeres. Perhaps Rashi understands the Gemara like the Me'iri.)
The Me'iri does not explain why the proper Chazeres for use as Maror should be one that was called "Chazeres" at the time the Torah was given. Since the requirement to give precedence to Chazeres is only a rabbinical recommendation, it should depend on what was called "Chazeres" during the times of the Mishnah.
Perhaps the Me'iri understands that the Rabanan made their enactment "k'Ein d'Oraisa," to resemble the Torah's requirement. Alternatively, perhaps he understands that the requirement to give precedence to Chazeres has its source in a Halachah l'Moshe mi'Sinai. (This does not appear to be the way Rashi learns the Sugya, because he writes (in DH Kol she'Nishtaneh) that the bitter herb must belong to the category of things that the Torah calls "Maror.")
(b) It seems that there is a dispute among the Tana'im in Pesachim with regard to the types of Maror that one may use. The Tana of the Mishnah there implies that only the five species listed may be used, since only those species were called "Maror" at the time the Torah was given. The Gemara here in Sukah seems to follow the opinion of that Tana, who says that Maror must be a specific type of herb, the name of which is "Maror." If it has a "Shem Levai," it is no longer "Maror." In contrast, the Gemara in Pesachim follows the opinion of Acherim that any bitter vegetable may be used for the Mitzvah of Maror. (NETZIV in MEROMEI SADEH)