Green’s Dictionary of Slang

(US) to die.

1875		M. Thompson Hoosier Mosaics 17: Berry Young took it awful hard ’bout the gal, an’ he’s been sort o’ sinkin’ away ever sence, an’ now he’s jist ready to wink out.
1920		Ade Hand-made Fables 274: His Pals came to see him just before he winked out.
1923		J.C. Goodwin ‘Criminal Sl.’ in Sidelights on Criminal Matters 165: He put a copper to bye-bye, and winked out in a horse’s night-cap.
1950		P. Hoskins No Hiding Place! 192/2: Winked out. Died.