Arry,
Jacker a term used to indicate someone or something has packed in or had enough, like the ferret has stopped hunting rats its jacked in, or the terrier has jacked to fox or a lurcher coursing or lamping.
Also used lot in the armed forces he jacked in training or jacked on a run, or tab/yomp (forced march) or a hard exercise in the field. Nowt to do with ferreting this mind but their you go.
PUD