The definition derives from old England where convicts used to tie bits of shirt around their toes and feet as a make shift sock, hence "toe rag" means scoundrel, criminal, thief, indencent/unlawful person etc. It is sometiem seen spelt Tow Rag because the original context has long since been obsolete.
A time when a man's hormones are in a state of inbalance. The male equivalent of PMS, although it happens less frequently, though generally still on a cyclic basis.
"I saw Chris walking home with a case of beer and a rented copy of 'The Deerhunter'. Dude's totally on his Man Rag."