A lot vs. Alot: 9 Grammatical Pitfalls
"one who avoids company," 1946; see lone. Apparently first in U.S. baseball slang (earliest reference is to Ted Williams).
Ted is likable enough in spite of his obsession with his specialty. He is something of a "loner," and he refuses to pal around with his teammates in off hours, but in the clubhouse he does his share of the talking. ["Life" magazine, Sept. 23, 1946]
late 14c., "having no companion, solitary," shortening of alone (q.v.) by weakening of stress or else by misdivision of what is properly all one. The Lone Star in reference to "Texas" is first recorded 1843, from its flag. Lone wolf in the figurative sense is 1909, American English.
An instance of eavesdropping or wiretapping: an occasional listen-in on the line (1940s+)