make (one’s) bones v. to kill a person as requirement for membership in a criminal gang, especially if it is one’s first murder; to become a made man; (hence) to earn a reputation. Editorial Note: This term is associated with organized crime, especially the Mafia or the mob. (source: Double-Tongued Dictionary)
Further reading
Colin from Los Angeles, California, is pondering the expression make no bones about it, which suggests the speaker is talking or acting with no hesitation whatsoever. The saying is inspired by the idea of literally finding bones in one’s food, since...
Doug in Madison, Wisconsin, remembers that when he was growing up in Philadelphia, his dad used the phrase the big mahoff to refer to someone important. This term that means “the big boss” or “the big cheese,” is largely localized to Philadelphia...