Spark/ spark off/ spark out/sparko

Spark or spark off meaning to start, trigger or initiate something dates from the early 20th century, from the obvious allusion of a spark starting a flame or fire. Spark out is a British colloquial expression for unconscious or fast asleep and dates from the 1960s. Sparko is a later version, dating from the 1980s, both deriving from the allusion to a dead or lifeless fire.