The word “slob” is a provincial term, and applied to banks of mud in the same way that the word “warp” is used to signify similar formations in the River Humber.
Second Report of the Commissioners appointed pursuant to the Act 5 & 6 William IV cap 67 for the improvement of the navigation of the River Shannon; with maps, plans, and estimates HMSO, Dublin 1837
Irish waterways history 
Good title Brian I though you were writing about the Irish version of Sir Les Patterson, Barry Humpheys character.
That might be Breakfast-roll Man https://www.youtube.com/watch?v=EIIWKA_h12Q
bjg