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!

or

Leopold: *drops something*
"you massive satchel of wank! It is NOT my day today!"

or

Hannah: stop being such a wank satchel and make me a coffee!

or

Henry: I have had the most satchy fucking week evaaarrr!

or

Emma: That guy last night was a total satch, he practically raped me! Lucky i was sobe as a judge...
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