In colloquial German there is a phrase, meant to counsel patience, that literally translates as 'Hold (on to) your pants'. That certainly predates an Americanism, I should think.I too am jolted by cavalry/calvary; I have often heard it mispronounced in songs. Another one- written by a friend of mine- sings about the 'tempetuous' sea. He must mean tempestuous or maybe he's thinking of 'impetuous'? I have never dared ask.
Oh- and how about 'mispronounciation'? I hear that too.
Ebbie