make (one’s) bones

make (one’s) bones
 v.— «After he suggested that Cuomo “made his political bones in Queens,” which has been rocked with scandal, he said he should have known it would set off opponents. Cuomo aides complained it was an ethnic slur, since “made his bones” is an expression usually connected with the Mafia.» —“The Race to Be 2nd—in Command Kavanagh—that’s Michael” by Laura Nicholson Newsday (Long Island, N.Y.) Oct. 20, 1986. (source: Double-Tongued Dictionary)