Gemara

(Mishnah): The following are Kinuyim (substitute words) for Korban: Konam, Konach, and Konas. Cherek, Cherech, Cheref are Kinuyim for Cherem. Nazik, Nazi'ach, and Pazi'ach are Kinuyim for Nezirus. Shevusah, Shekukah, or vowing 'b'Mohi' are Kinuyim for Shevuah.

(R. Yochanan): Kinuyim are from Nochri languages;

(Reish Lakish): Chachamim concocted them for people to use when vowing.

Question: Why did they concoct them?

Answer: They did not want people to say "Korban", lest one come to say "Korban la'Shem", and come to say only "la'Shem" without "Korban". If so, he mentioned Hash-m's name in vain!

Suggestion: R. Yochanan and Reish Lakish argue like the following Tana'im:

(Beraisa - Beis Shamai): Kinuyim of Kinuyim are binding.

Beis Hillel say, they are not binding.

Suggestion: Beis Shamai holds that they are from Nochri languages (and also Kinuyei Kinuyim are used to denote Korban or Cherem...) Beis Hillel hold that Chachamim concocted Kinuyim, but not Kinuyei Kinuyim.

Rejection #1: All agree that Kinuyim are from Nochri languages. Beis Shamai hold that Nochrim also use Kinuyei Kinuyim, and Beis Hillel hold that they do not.

Rejection #2: They argue about whether or not we decree to forbid Kinuy Kinuyim.

3a: The Tana (of the Mishnah 2a) taught Kinuyim first because they are mid'Oraisa.

Question: This is like the opinion that Kinuyim are from Nochri languages. According to the opinion that Chachamim invented Kinuyim (also they are mid'Rabanan), how can we answer?

Rishonim

The Rif brings the Gemara (10a) verbatim.

Rambam (Hilchos Nedarim 1:16): There are places where people speak improperly and call something by the wrong name. We follow the substitute name. All Kinuyim for Korban are like Korban. If one said 'they are Alai (upon me) Konam', 'Konach', or 'Konaz', these are Kinuyim for Korban. The same applies to everything similar. We follow the way commoners speak at that time and in that place.

Radvaz: It is not clear if the Rambam rules like R. Yochanan or Reish Lakish. Presumably, he follows R. Yochanan against Reish Lakish. However, he found it difficult why Nochri languages should work. Rather, it is because there are people who speak improperly. Therefore, it applies even where there are no Nochrim, or where they have no word for Korban. We follow the substitute name because Nedarim follow the way people speak. It does not matter whether or not the one who vowed can speak properly.

Rambam (17): Kinuyei Kinuyim are permitted.

The Rosh (1:9) brings the Mishnah.

Question: R. Yochanan holds that Kinuyim are from Nochri languages. If so, why does our Mishnah bring these specific examples? It should say that a Neder in any language is valid!

Answer #1 (Ran 2a DH Kol, citing R. Yehudah b'Ribi Chisdai): The Mishnah teaches a bigger Chidush. Not only proper translations (of Neder, Nezirus...) in other languages are valid. Rather, even these improper expressions, which came from Lashon ha'Kodesh but were mangled, are valid. One might have thought that they are invalid, for they are not proper speech. The Mishnah teaches that they are valid, for Nochrim use them. All the more so, other languages work. The Yerushalmi confirms this explanation.

Answer #2 (Ri, in Tosfos 2a DH Kol): If one vowed with one of the Kinuyim in the Mishnah, it is valid even if he did not understand it. Any other Kinuy works only if he understood it.

Question (Tosfos Yom Tov Nazir 2:1 DH Nazik): How can it take effect without understanding? His mouth and heart must be equal (Terumos 3:8)!

Answer (Orach Mishur on Tosfos Nazir 2a DH Nazir): Tosfos must hold like those who say that Devarim sheb'Lev count only when he did not say the words he wanted to say. If one said the words he wanted, but intended that it not take effect, it takes effect (Mordechai, Tosfos Shevu'os 26b DH Gamar, and Shulchan Aruch YD 211:1).

Question: Tosfos (ibid.): According to the opinion that Kinuyim are mid'Rabanan, how can a Nazir bring Korbanos for Nezirus mid'Rabanan? It is not difficult how one is liable for Bal Te'acher for a Neder mid'Rabanan.

Answer #1 (Tosfos): Indeed, all agree that Kinuyei Nezirus are from Nochri languages. They argue only about Kinuyim for Nedarim. This is why the Gemara in Nazir (2b) did not ask according to Reish Lakish why the Mishnah (Nazir 2a) begins with Kinuyim.

Rejection (and Answer #2 - Ri, in Tosfos, ibid.): Often, the Gemara asks a question in one place, and not elsewhere! Rather, Chachamim have the power to make their enactment like Torah Nezirus.

Answer #3 (Ri, ibid., and Tosfos Nazir 2a DH Nazir): Since he wants to accept Nezirus, and he knows that Chachamim concocted this expression for Nezirus, it is a full acceptance.

Answer #4 (R. Yechiel in Tosfos, ibid.): Reish Lakish did not mean that he brings Korbanos for Nezirus through a Kinuy. Rather, he is lashed if he transgresses Nezirus.

Answer #5 (Orach Mishur ibid., b'Sof): Reish Lakish holds that the entire Isur of offering Chulin in the Mikdash is mid'Rabanan (Nazir 29b).

Poskim

Shulchan Aruch (YD 207:1): Kinuyim for Nedarim are like Nedarim. If one said 'this loaf is Alai Konam', 'Konach', or 'Konas', it is forbidden to him. Similarly, in every place we follow the way people speak. If they have a Kinuy for Neder and one vowed with it, it is a Neder.

Beis Yosef (DH u'Mah she'Chosav): The Gemara connotes that we follow the time and place. If people use a word, it is valid, even if Chachamim did not discuss it. If no Am ha'Aretz recognizes a Kinuy that Chachamim discussed, it does not work. It seems that the Rambam holds like this.

Taz (1): Konam is a Kinuy. In Kol Nidrei we say 'Konamei v'Kinusei v'Chinuyei.' The first two are the most common Kinuyim, and v'Chinuyei includes all other Kinuyim.

Rema: If one does not know the expressions that Chachamim spoke about, even if he vowed by them, it is void.

Gra (3): This is because his mouth and heart are divided. This is unlike Tosfos (Nedarim 2a).

R. Akiva Eiger: If he wanted to vow with the Kinuy, it is valid, even if he does not understand what it means. His mouth and heart are equal! The Rashba (Reish Nedarim) agrees.

Shulchan Aruch (ibid.): Kinuyei Kinuyim, i.e. a Kinuy that is very far from the proper word, is invalid.

Rema (237:1): A Shevu'ah takes effect in Lashon ha'Kodesh or any other language.

Source (Gra 2): R. Yochanan holds that Kinuyim are from Nochri languages.

Shach (2): Maharam me'Rotenburg (Teshuvah 6) says that if one mentioned Hash-m's name in another language, this is a Yad for Shevu'ah, even if he did not say 'Shevu'ah'.