Come home and I hit it hard, and she gives me head that’s concussion
When he comes home he
hits it hard
Which can either be referring for instance to ripping or smoking marijuana from a bong pipe
The second part of the lyric is referring to receiving oral sex or head
Referencing earlier when he mentioned hitting it hard, a hard hit on the head can often result in a medical condition called a concussion or a bruise on the brain.
So the metaphor concussion is used to describe how hard she goes when she gives head, in other words, her head is amazing.
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