How do you say “Beat a dead horse” in German?

The English idiom 'to beat a dead horse' (or 'flog a dead horse' in British English) describes the futile effort of trying to revive or debate a matter that is well past changing. German handles this nuance through different idioms depending on whether the emphasis is on arguing a point or maintaining a doomed project. When someone keeps arguing or dwelling on an issue that everyone else considers closed, native German speakers universally say 'auf etwas herumreiten' ('to ride around on something', i.e., to harp on it) or 'alte Kamellen aufwärmen' ('to reheat old caramels').

If the situation involves persisting in an unworkable project rather than merely debating it, modern German often uses 'ein totes Pferd reiten' ('to ride a dead horse'), borrowed from modern management philosophy. However, never translate 'beat' literally into 'ein totes Pferd schlagen' or 'prügeln', it immediately reveals non-native phrasing. Stick to 'darauf herumreiten' when telling someone to drop a settled debate.