From Longman Dictionary of Contemporary Englishgristgrist /ɡrɪst/ noun → (all) grist to the mill
Examples from the Corpus
grist• In fact, all the events' of daily life are grist to the mill of these popular singers.• Writers of all ages see particulars of their lives as grist for the mill, as resources for writing.• If the guest was a bore, he or she unwittingly became grist for the act.Origin grist Old English “grain to be broken into small pieces” 