E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A variant of Od rot em! The first word is a minced form of the word God, as in Ods blood! Od zounds!=Gods wounds, Ods bodikins, etc. (See ODS.) A correspondent in Notes and Queries suggests [May] God out-root them! but we have the words drattle and throttle (to choke) which would better account for the a and the o, and which are also imprecations.