Well, technically it should be “I is for Iuppiter”, but since the Latin I and J are interchangeable I decided to cheat a little. Sorry =(
Ah, Iuppiter…where to begin?
I guess I could start by saying that Iuppiter is the King of the Gods and the head of the powerful Capitoline Triad (Iuno and Minerva are the other two deities of this Triad). He started out as a sky god, ruling over the heavens and making his will known with thunder and lightning. Like with all deities, he has more than just a few attributes in his domain: he is also a domestic god, a protector god, a god of war and the spoils of war – and, as a bonus, the patron of bakers. He was the patron of the Romans, because they gave more offerings to him than any other deity. And those are just a few. In the later Republic he was identified with the Greek Zeus. He is, for the most part, a friendly god, and it is from his name that we get the word “jovial.”
For those linguists and/or Hellenic polytheists out there who are reading this, you may recognize his name as extremely similar to that of the vocative Zeu Pater, or Father Zeus. This is no coincidence: both names apparently come from the Indo-European vocative Dyeu pater. And according to the 19th century philologist Georg Wissowa, Iuppiter’s name was originally Dieus-pater, which later got shortened to Diespiter.
Iuppiter had his own priest, an important man called the flamen Dialis. The wife of this flamen was called the flaminica Dialis. There were some strange customs that the flamen Dialis had to follow: he could not remove his trademark pointy hat while outdoors, swear any oaths, or be absent from his bed for more than two nights in a row. The reason for the former was supposedly because he didn’t want to risk offending Iuppiter by appearing “naked” in the sight of the god. During the waning years of the Empire, however, the post of the flamen Dialis went unfilled: from approximately 86 BCE to 11 BCE the other pontifices, or priests, of Rome were responsible for performing the duties of this office.
There are a few surviving myths of the King of the Gods as well. In one myth, Iuppiter is said to be the twin of Iuno and the son of Fortuna Primigenia (although there is another version of this myth that says that he is the father of Fortuna Primigenia). Later, when he became identified with the Greek god Zeus, he was seen as the brother of Neptunus and Pluto and the son of Saturnus. He was also seen as the equivalent of the Etruscan god Tinia.
In another myth, he enters into a battle of wits with the second King of Rome, Numa Pompilius, resulting in the ancile – or angle-less – shield being dropped from the sky as a symbol of the power that the Romans would later hold. He later struck down Tullus Hostilius, the third King of Rome, after Tullus did not dutifully perform sacrifices, and gave the fifth King, Lucius Tarquinius Priscus, a sign that he would become King.
The sacred animal of Iuppiter was the eagle. Because of this, the standards of the Roman army bore the eagle, and it was considered an unspeakable disgrace to lose one’s aquila, or eagle-standard, to the enemy. Animals that were sacrificed to Iuppiter were the castrated bull, lamb, and ram, and all of these victims were supposed to be white in color.
Along with the sacred animal, Iuppiter had sacred days of the calendar. These included the Ides (the 13th or the 15th of the month) and the nundinae, or market days that occurred every 9th day. He had several feast-days as well, known as the epula Iovis.
Iuppiter has many, many epithets – too many for me to list here without at best tripling the size of this post. Perhaps his most well known epithet is Optimus Maximus, or the Best and Greatest, and this role of Iuppiter had a temple on the Capitoline Hill.