‘Knuckler’ Moren”. (In list of players). The Philadelphia Inquirer, March 30, 1908.
“…. even such veterans as Manager Murray and Captain Gleason say that in all their long careers they have never seen anything like Richie’s sepentine [sic] twister and Moren’s ‘knuckler’.” The Altoona Times, March 31, 1908, p9
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1913. “It was [Eddie] Cicotte who brought the knuckler into the spotlight of the national game” (Williamsport [Pa.] Gazette and Bulletin, March 17; Peter Morris).