Referring to a wallet filled with tons of cash. West coast rapper Sayef Aranki aka Analyst founded the term. He's said to have first used the term in one of his tracks entitled "Victory Freestyle."
Victory Freestyle: "I stay starvin' thats the way I keep my wallet obese"
Term used in sentence: "Yea I'm slim, but I got an obese wallet"
And dying in yo' bed many years from now, would ya be willing ta trade all da days from dis here day ta dat fo' one chance, just one chance, ta come back here as young men an' tell our enemies dat dey may take our lives but dey will never take our freedom ... YUB NUB!