1769, "pin passed through the eye of a rope, strap, or bolt to hold it in place," a nautical word of uncertain origin, perhaps a frequentative form of tog "tug." As a kind of wall fastener it is recorded from 1934. Toggle bolt is from 1794; toggle switch, the up-and-down sort, first attested 1938. In computing by 1979, in reference to a key which alternates the function between on and off when struck.
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