>You might not wish to know what "hump" means here.<

Oh, I think gutter-dwelling Jackie would wish to know!

But the difference between 'yomp' and 'hump' (in Jackie's sense) is that yomp is intransitive and hump is transitive.
I feel like heading back to 'Dried Words' - this is another case where the one word has more than one meaning inherent in it. To be hiking and to be heavily laden. No object required. One just yomps acros the countryside and an overfilled backpack appears as if by magic in the listener's (reader's) mind's eye.