thank you so much for asking, dr. bill. originally it was formed from grunt plus the diminutive or frequentive ending and had the sense of uttering a grunt; from there it shifted in meaning to grumble or complain. but this usage died out and the word has returned as a back-formation from disgruntle and meaning the opposite thereto; i.e., to put in good humor. but what goes around comes around in this case, as we must ask ourselves "when is it that pigs grunt"?