Main Entry: grun·tle Pronunciation: 'gr&n-t&l Function: transitive verb Inflected Form(s): grun·tled; grun·tling /'gr&nt-li[ng], 'gr&n-t&l-i[ng]/ Etymology: back-formation from disgruntle : to put in a good humor were gruntled with a good meal and good conversation -- W. P. Webb
Obviously bad food and poor conversational skill...