Lil Jon Reveals Freak Childhood Accident Behind His Signature Sunglasses

Lil Jon has spent decades rocking his signature sunglasses ... but it turns out the look has a pretty painful backstory involving a needle to the eyeball.

The "Turn Down for What" rapper reveals in his upcoming memoir, "I Only Shout So You Can Hear Me," that he accidentally stabbed himself in the eye with one of his mother's insulin syringes when he was just 6 years old.

According to People, Jon had watched his diabetic mother give herself insulin shots ... and one day, curiosity got the best of him when he grabbed a syringe to see what the air would feel like against his eye.

Instead, he accidentally jabbed himself in the eyeball ... leaving him with a traumatic cataract and forcing him to undergo multiple surgeries, including a corneal transplant.

Things weren't much easier at school ... Jon says he had to wear a metal eye patch and was bullied by other kids, which made him shy.

The childhood injury eventually left him with a lazy eye, and although he underwent another surgery to correct it, he continued wearing sunglasses ... turning a painful childhood memory into one of hip-hop's most recognizable looks.

Jon says the experience also lit a fire under him to prove his doubters wrong ... and judging by his career, we'd say he got the last laugh.