Its meaning derrives from a bag used to store cum or a whore for same purpose.
1. An offensive term used to describe someone, something or a situation...
2. A bantersaurus way in which to describe a scrotum
(The phrase can also be reversed to "satchel of wank", or shortened to just "satchel" or "satch", maybe even satchy)
Barry: Mrs Stewart is a massive wank-satchel, i hope she dies!
Leopold: *drops something*
"you massive satchel of wank! It is NOT my day today!"
Hannah: stop being such a wank satchel and make me a coffee!
Henry: I have had the most satchy fucking week evaaarrr!
Emma: That guy last night was a total satch, he practically raped me! Lucky i was sobe as a judge...