This is very old slang, but is still used occasionally It refers to a person who falsely claims to have medical knowledge or qualifications, especially one who dispenses pills, potions and ointments that have curative properties. The word comes from the Middle Dutch word kwaksalver which means one who sells salves and ointments. Although seldom used nowadays quacksalver is the origin of the term quack which means pretty much the same thing.

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.