(Slang.) To «have the drop on» is toforestall, gain advantage over, especially by covering with arevolver.
It is curious that while an American magazine calls this phrase Australian (see quotation), the `Dictionary of Slang' – – one editor of which is the distinguished American, Godfrey C. Leland – – says it is American. It is in common use in Australia.
1894. `Atlantic Monthly,' Aug., p. 179.
«His terrible wife, if we may borrow a phrase from Australia,`had the drop on him' in every particular.»