Origin of get-out
Word Origin and History for as all getout
to indicate a high degree of something, attested from 1838.
Idioms and Phrases with as all getout
as all getout
To the ultimate degree, as in She made him furious as all getout. The American writer Joseph C. Neal had it in his Character Sketches (1838): “We look as elegant and as beautiful as get out.” Today it always includes all. [Colloquial; first half of 1800s]