ok, since most of you think that it came from rap music.. heres the facts:
Jea, is a word that was ripped off of Rastafarian God, Jah.
Jah: Gods name as based on the Bible, commonly refered to as Jehovah, though the abbreviation is taken also from the Bible.
Commonly extracted in Rasta beats, which amongst other religions recoginize gods name as being Jehova.
After time, the name Jah Rastafari a.k.a Lion of Juddah was mis used as Jea. Its merely is the same word, with the same sound just typed differently. After Bob Marley essentialed formed reggae culture of music, the influence of Jah got out.
Now, kids who do not even know what this word means, mistake jah for jea, and have no idea where it comes from and just think its the same as yeah , replacing the y with a j and dropping the h.
Atleast know where the term comes from before you use it exessivly (sp?) please. Show some respect to the rastafarian culture.
* source http://www.urbandictionary.com/define.php?term=Jah