also alchy, 1841, "an alcoholic drink" (also "alcoholic drink personified"), a slang shortening of alcoholic liquor first attested in temperance publications. As "a drunkard" (short for alcoholic (n.)) it is suggested by 1888.
"What is his name?"
"Hall is his real name; but they call him Alky, because he drinks — Alky Hall; alcohol, you know. But he's given up drinking now, since I told him about temperance and lent him my Sargent's 'Temperance Tales.' I'll warrant you he'll never drink another drop." [Joseph Kirkland, "The McVeys," 1888]