It's the ZM, keep SG deleted
Art's been official since kick beats as a fetus

from Zen Master Griff – RG Battle Round 3 Lyrics on Rap Genius

Meaning

ZM = Zen Master, and to add SG would make Z'MSG', part of the acronym representing what is known as a chemical for artificial flavoring. This explains the subtle wordplay in the next line, “Art’s been official” as opposed to artificial.

There’s also some imagery of me making music whilst kicking my mother’s stomach…

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