“Old Dick Hingham of the Chicago White Stockings was what the fans call a ‘streak’ hitter. When his streak hit him he’d drive them into the bleachers or somewhere else just as good, but on his off days he fanned as gracefully as a debutante at her coming out ball.” Byron Clarke, Minneapolis Star Tribune, January 12, 1908, p32 (Wire service article)
“Snodgrass is a streak hitter. Weeks at a time he can’t hit a thing, and all of a sudden he begins, and, no matter what you serve him, he laces it safe.” Grover G. Alexander. Tacoma Times, September 22, 1913, p1
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1914. “[Joe] Jackson is what we call a streak hitter. He bats like a fiend for a time and then his work drops off” (Ty Cobb, Busting ’Em and Other Big League Stories; Peter Morris).