If Esav's first wife was called Ada bas Eilon, why, in Parshas Toldos (Bereishis 26:34), does it refer to her as "Bosmas bas Eilon"?
Rashi: Because she sacrificed incense to Avodah Zarah, as Rashi explains there (Pasuk 5).
If Esav's second wife was called Aholivamah bas Anah, why does the Pasuk there refer to her as "Yehudis bas Be'eri"?
Rashi: To trick his father into believing that she did not believe in Avodah Zarah. 1
Rashbam: Yehudis bas Be'eri died without children. After Esav moved to Har Se'ir, he married into the Chori, i.e. Aholivamah bas Anah bas Tziv'on ben Se'ir ha'Chori. Also Timna, Elifaz' concubine, was from Bnei Se'ir. Since Aholivamah was Esav's last wife, she is mentioned last.
The Ramban queries Rashi (a) about her father's name which one Pasuk gives as Anah, and the other, as Be'eri? (See Sifsei Chachamim), and (b) as to why he presents 'Bosnas bas Eilon' as her real name, and 'Bosmas bas Be'eri' as a description of her deeds? Moreover, asks the Sifsei Chachamim, why did he not also change the name of his first wife, Bosmas, in order to trick his father? (See his answer). Another problem with Rashi is why the Pasuk here changes the order of Esav's first two wives?
Anah was Tziv'on's son (as recorded later, in Pasuk 24). In any event, how can Aholivamah have been the daughter of both Anah and Tziv'on?
Rashi: Because she was the product of the illicit relationship between Tziv'on and Anah's wife (his daughter-in-law), in which case she was the daughter of Tziv'on and of Anah's wife. 1
Ramban (on Pasuk 24) #1: The Anah mentioned here was the nephew of Anah mentioned in Pasuk 24. 2
Hadar Zekenim: A granddaughter can be called a daughter. 3
Moshav Zekenim (14) and Ramban (24) #2, from Pesachim 54a: Anah had Bi'ah with his mother, and Aholivamah was born. 4
Moshav Zekenim (14, from Bava Basra 115b): Anah was a female. Tzivon fathered her through his own mother. Anah is listed among heirs of Se'ir, for she inherited in place of her father Tziv'on, who had died. It says "Hu Anah" (masculine) because she inherited like a son. 5
This teaches us that Esav's family was riddled with Mamzerus (Refer to 36:12:2:3*). She is called Bas Anah, for people assumed that she is Anah's daughter - Moshav Zekenim 24. (The Ramban, later in Pasuk 25, cites this explanation in the name of the Midrash, but concludes that it does not fit well into the Pasuk.)
She is called Bas Tziv'on because she inherited in place of her grandfather Tziv'on. I.e. there were no living sons or grandsons of Tziv'on - Dishan (verse 26) is Se'ir's son (verse 21), and not Anah's son, and the brother and son of Anah (Dishan and Ayah) died without children. I infer so from Moshav Zekenim (14), from Bechor Shor (PF). Refer to 36:2:3:5*.
Ramban: She is called Bas Tziv'on, for people assumed that she is Tziv'on's daughter.
Anah had a brother Ayah. Ayah should have inherited, and not her! We must say that Ayah died without children. The Torah does not list children from him.
Rashi says that Aholivamah bas Anah bas Tziv'on ha'Chivi is Yehudis bas Be'eri ha'Chiti. Chivi and Chiti are different nations! And below, Tziv'on is listed among "Bnei Se'ir ha'Chori." Chori is another nation!
Moshav Zekenim, citing R. Yitzchak: Really, [Tziv'on] is a full Chiti. He is called Chivi and Chori for a Drashah, like it says in Shabbos (85a, how they knew what is good to plant in each place). Chori were Meri'ach (smelled) the earth. Chivi would taste the land like a Chavya (snake. It eats earth.) This forced the Gemara to expound these names more than other names of nations.
רש"י: אהליבמה היא יהודית: למה לעיל היא נקראת "בת בארי" וכאן "בת ענה"?
גור אריה: עשיו שינה גם את שם אביה כי 'ענה' היה ידוע כממזר.
רש"י: אהליבמה היא יהודית: לעיל כתוב שהיא חיִתית וכאן כתובת שהיא חיוית?
גור אריה: החִוי היו הגרועים שבבני חם (כי חִוי פרושו נחש) ולכן אמר עשיו שהיא חיִתית.
רש"י: שבא צבעון על...אשת ענה ויצאת אהליבמה: אם כך למה כתוב שהיא בת ענה?
גור אריה: היא נראתה בתו של ענה אבל באמת הייתה בת צבעון.
רש"י: שבא צבעון על...אשת ענה ויצאת אהליבמה: אולי היא בת צבעון ושם אמה ענה?
גור אריה: בסתם התורה לא מייחסת את הבת לאם אלא כשיש סיבה לכך.
רש"י: שבא צבעון על...אשת ענה ויצאת אהליבמה: אולי להפך- ענה בא על אשת צבעון?
רא"ם: עדיף לומר שצבעון הוא זה שנתקלקל פעמיים- כאן ולקמן (פסוק כד) כשבא על אמו- אשת שעיר, ונולד ענה.
גור אריה: אילו היה ענה האב האמיתי, אחר שייחסנו אותה אליו, שוב אין ליחס אותה אל צבעון שרק נראה כאביה.
רש"י: שבא צבעון על...אשת ענה ויצאת אהליבמה: למה לא פירשו שצבעון היה אבי אביה של אהליבמה ובני בנים כבנים?
גור אריה: אם כך, היה צריך לכתוב 'בת ענה בן צבעון'.
גור אריה: כשבא ליחס את התולדות אל מולידיהם ראוי יותר לייחסם אל אביהם, והיחוס אל הסבא הוא לא היחוס האמיתי.