Why does “T.L.” mean a compliment?

The letters T.L., when used to mean a compliment, are the abbreviation of trade last. These words acquired the meaning of an offer to give a compliment in exchange for one from the playful custom of a person saying to one of the opposite sex, “I have a trade last for you,” meaning that if you will tell me something nice you heard about me, I will tell [458] you a compliment I heard about you. Sometimes the second element in trade last is written lassie or me-lass. The following from the Chicago Tribune illustrates the popular use of the term: “Grade, who loves flattery, is going to be mad in a minute. She wants a trade last and her best boy is about to tell her he heard so and so say she was remarkably well preserved.”