“There was only one way to settle this ‘mouthing,’ which had been running on for so many weeks and that was playing and seeing which was the superior nine. For weeks it has been ‘chin music,’ to use a common saying, and now the talk has taken another turn.” Brooklyn Daily Eagle, October 31, 1865, p2 (Second sense of term: “Impudent talk from a player, coach, or umpire, taking the form of sarcastic allusions, irritating comments, complaints, joking, jockeying, fault-finding, arguing.”)
“No pitcher should be permitted to delay the game, and annoy the batsman by a series of balls short of the home base, or over the player’s head, or close to his body … Indeed, if the Lansingburgers do not furnish less ‘chin music’ in their game with the Mutuals today, they may induce trouble.” “The World (New York), September 25, 1867, p8 (First sense of the term: “A brushback or knockdown pitch that passes close to the batter’s jaw, thrown so high and inside that the batter supposedly can hear it ‘buzz or sing.’”)
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1868. “[The Athletic club of Philadelphia] are active, muscular, and are disposed to indulge freely in ‘chin music’ towards one another, which does not help their game” (Detroit Advertiser and Tribune, June 23; Peter Morris). (Second sense of term: “Impudent talk from a player, coach, or umpire, taking the form of sarcastic allusions, irritating comments, complaints, joking, jockeying, fault-finding, arguing.”)
