Knuckle Ball (1907)

“[Lew] Moren, a young pitcher with Philadelphia, has invented a drop curve called the knuckle ball and makes it work very prettily.” The Racine Daily Journal, April 30, 1907, p7

Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1908 (New York Evening Journal, March 24; Edward J. Nichols).