Put Someone's Lights Out Meaning

Example : 1981 Sept. 16, "More than 300 million to see THE fight tonight," Beaver County Times, p. C1 (retrieved 12 Nov 2015):  "He's taken an awful lot of punches in his last few fights and if Thomas hits him like that, he'll put his lights out. It'll be like a blackout."1984 Aug. 28, Bert Rosenthal, "Hagler looks forward to Garden visit," Kentucky New Era, p. C1 (retrieved 12 Nov 2015):  "The last time I fought Mustafa, I just wanted to give him a beating. . . . This time, I want to put his lights out."1996 Dec. 31, Bill Copeland, "True love is where you find it," Sarasota Herald-Tribune, p. 4E (retrieved 12 Nov 2015):  [H]e knew every trick in the books, combatwise, and "could put your lights out with a simple sustained pressure on a carotid nerve."