This word is used by Mr. Lorry to describe his work situation to Miss Lucie Manette in Book I Chapter Four of this great novel. He is trying to explain why he is not able to express feelings and can have no time for them, describing Tellson's House and his employment as a job that crushes all such sentiment from his body:
"Feelings! I have no time for them, no chance of them. I pass my whole life, miss, in turning an immense pecuniary Mangle."
Pecuniary in this context means of or relating to money, focusing on the way in which Tellson's exists for one purpose alone: to make money. Anybody working for Tellson's thus finds themselves stripped of human emotions and decency, though of course Mr. Jarvis Lorry manages to escape this fate and determines to leave Tellson's so as to cling on to his humanity.