What does the expression "Back door man" means ?

Question

Popular in the 60's, you can here it in some Led Zeppelin's songs and The Doors' song "Back door man".

Answer 1

not your main man

Answer 2

the phrase "back-door man" refers to a man having an affair with a married woman, using the back door as an exit before the husband comes home.

Answer 3

It means someone has a lover on the side who uses the back door so he won't be caught by the husband or boyfriend who uses the front door.