E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
To run away, to be scattered in rout. The Scotch apply the word to the milk spilt over the pail in carrying it. During the late American war, the New York papers said the Southern forces were skedaddled by the Federals. (Saxon, scedan, to pour out; Chaldee, scheda; Greek, skedao, to scatter.)