Definition of "fatted"

For whan they were hongry they knewe god / And whan theyre belyes were fylde & fatted / they forgid ydoles & were ydolatrers

31 March (1474) Jacobus de Cessolis, (fl. 1288-1322) The Game and Playe of the Chesse (De ludo scachorum), William Caxton and Colard Mansion Bruges.