"fuel residue, solid product of the carbonization of coal,"an important substance in metallurgy, 1660s, a northern England dialect word, perhaps a variant of Middle English colke "core (of an apple), heart of an onion" (c. 1400), also "charcoal" (early 15c.), a word of uncertain origin. It seems to have cognates in Old Frisian and Middle Dutch kolk "pothole," Old English -colc, in compounds, "pit, hollow," Swedish dialectal kälk "pith." Perhaps the notion is the "core" of the coal, or "what is left in the pit after a fire."
soft drink, 1909, a popular shortening of the brand name Coca-Cola, perhaps influenced by the earlier slang use of coke for cocaine (another popular early name for the soft drink was dope).
slang shortened form of cocaine (q.v.), by 1902, American English.