All 3 Uses of

impoverish
in
A Tale of Two Cities

Miss Pross's friendship being of the thoroughly practical kind, she had ravaged Soho and the adjacent provinces, in search of impoverished French, who, tempted by shillings and half-crowns, would impart culinary mysteries to her.†
Chpt 2.6 *

impoverished = poor, or (more rarely) made poor

Monsieur Gabelle had held the impoverished and involved estate on written instructions, to spare the people, to give them what little there was to give—such fuel as the heavy creditors would let them have in the winter, and such produce as could be saved from the same grip in the summer—and no doubt he had put the fact in plea and proof, for his own safety, so that it could not but appear now.†
Chpt 2.24

Happily, however, there was sleep in Beauvais that night to help them out of it and they passed on once more into solitude and loneliness: jingling through the untimely cold and wet, among impoverished fields that had yielded no fruits of the earth that year, diversified by the blackened remains of burnt houses, and by the sudden emergence from ambuscade, and sharp reining up across their way, of patriot patrols on the watch on all the roads.†
Chpt 3.1

Definition:

make someone poorer; or make something less valuable