Even though I would say that I am quite fluent in English, I encounter new words all the time. I hadn’t heard of yomping before I read these lines from The Salt Path.
The definition of yomp according to the Cambridge English Dictionary is as follows.
Yomp: (often of soldiers) to walk quickly and energetically, usually while carrying a lot of equipment.
I think yomping sounds very bouncy and impulsive – not a walking style I’d link to soldiers. But, sadly, it is not up to me to decide what words mean.