1) To wear your pants down so low that your undergarments are visible

2) Used in prisons usually to symbolize availability or as an invitation to get it in the ass from a fellow inmate.

A phrase to describe someone who is cognitively degenerating. Synonym of "going off the deep end". Can have varying degrees of severity.

Reference to the song "Hey You" by Pink Floyd. The line "and the worms ate into his brain" makes no sense in an otherwise linear and literal narration throughout the lyrics.