I got my thumb on Hip Hop, and my foot in the back of your ass
“I got my thumb on Hip Hop” is pretty obvious. Ever since Kendrick dropped good kid, m.A.A.d city, the face of Hip Hop changed. He has his thumb on it or under his power, command, and control (pun intended).
The second portion, “and my foot in the back of yo ass”, is pretty obvious as well. Kendrick dominates any and all competition, so he sticks his foot up their ass, and shows utter disrespect and kills their threats off. Also, “ass” is a continuation of the pin the tail on the “donkey” line. Having a foot up one’s ass is also a clear reference to Ice-Cube’s famous line on Gangsta Gangsta
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