means To poach is either to cook food gently in barely simmering liquid, or to take something illicitly — game, talent, or ideas — that isn't yours to take.

from Two threads twist together here. The cooking sense comes from the Old French 'poche,' a pouch or pocket — a poached egg is one cradled in a little pocket of its own white, the yolk tucked inside like coins in a purse. The thieving sense likely shares that same 'pocket' root: to poach was to stuff stolen game into a bag, possibly via the idea of 'pocketing' what wasn't yours. So both meanings circle the same image — something nestled where it's held close — which is why English never bothered to keep them apart.