Belphegor

The name Belphegor is a corruption of the biblical name Baal-Peor, the god of the Moabites. Numbers 25 describes that when Israel was in the northeast corner of the plains of Moab (called Abel-Shittim), they had illicit relations with the Maobite women and sacrificed to their god. As punishment, Moses all the Israelites who had sacrificed to Baal-Peor were to be killed. This slaughter amounted to 24,000 deaths. (Num 25:9)

Several other passages seem to refer to the event:

“Your eyes have seen what the LORD has done in the case of Baal-peor, for all the men who followed Baal-peor, the LORD your God has destroyed them from among you.” – Deuteronomy 4:3
“They joined themselves also to Baal-peor, And ate sacrifices offered to the dead.” – Psalm 106:27-29
“I found Israel like grapes in the wilderness; I saw your forefathers as the earliest fruit on the fig tree in its first season. But they came to Baal-peor and devoted themselves to shame, and they became as detestable as that which they loved.” – Hosea 9:10

He may be identified with Chemosh, the Moabite war god who fought against the Israelites.

“Woe to you, Moab! The people of Chemosh have perished; For your sons have been taken away captive And your daughters into captivity.” – Jeremiah 48:46

He was sometimes depicted as a phallus, a cone, a pillar, or a tree branch. As male, he was the sun god. As female, a moon goddess sometimes associated with Ishtar. As Baal-Peor, he was androgynous. As Chemosh, he would have been worshipped by Solomon.

“Then Solomon built a high place for Chemosh the detestable idol of Moab, on the mountain which is east of Jerusalem, and for Molech the detestable idol of the sons of Ammon.” – 1 Kings 11:7
“The high places which were before Jerusalem, which were on the right of the mount of destruction which Solomon the king of Israel had built for Ashtoreth the abomination of the Sidonians, and for Chemosh the abomination of Moab, and for Milcom the abomination of the sons of Ammon, the king defiled.” – 2 Kings 23:13

Belphegor - Dictionnaire Infernal

Dictionnaire Infernal – Collin de Plancy (1863) (paraphrased)
Known as the demon of discoveries and of ingenious inventions, Belphegor is said to appear as a young girl and to give wealth. He was worshipped by the Moabites as Baalphegor on Mount Phegor. Some rabbis claim that he must be worshipped on a toilet, with offerings being the residue of ones’ digestion. This has led some to conclude that Belphegor is the god Pet (Fart) or “Crepitus,” while others believe that he is Praipus. Selden is cited by Bainier as reporting that human victims are to be offered to him, and that his priests partake of the flesh. Wierus wrote that he always has an open mouth, attributing it to the name Phegor, which according to Leloyer means “crevice” or “split,” and refers to when he was worshipped in caves and people threw him offerings through an air hole.