As a writer of local color, Mark Twain often used colloquialisms and regionalisms that were unfamiliar to many of his readers. When some of these expressions eventually caught on in the language at large, they were traced back to Twain. For example, he is credited with the first printed use of blow up ("to lose self-control") in 1871, of slop ("effusive sentimentality") in 1866, and of the phrase sweat out ("to endure or wait through the course of") in 1876. Hard-boiled is documented as being first used by Twain in 1886 as an adjective meaning "emotionally hardened." Apparently, Twain and others saw the boiling of an egg to harden the white and yolk as a metaphor for other kinds of hardening.