Yours, Etc.: Origins and Uses of 8 Sign-Offs
"to run away," 1861, American Civil War military slang, of unknown origin, perhaps connected to earlier use in northern England dialect with a meaning "to spill." Liberman says it "has no connection with any word of Greek, Irish, or Swedish, and it is not a blend" [contra De Vere]. He calls it instead an "enlargement of dial. scaddle 'scare, frighten.'" Related: Skedaddled; skedaddling. As a noun from 1870.
To run away; flee; fly; depart hastily: the verb ''to skedaddle,'' which was revived during the war to suggest precipitous flight, and has held its own ever since
[1861+; origin unknown; perhaps fr an attested Scots dialect sense, ''spill,'' which could suggest ''scatter, disperse''; the example from 1884 supposes an earlier origin]