Battle sign is an eponymous term given to mastoid ecchymosis (bruising of the scalp overlying the mastoid process) and is strongly suggestive of a base of skull fracture, most commonly a petrous temporal bone fracture.
History and etymology
Mr William Henry Battle (1855-1936) was an English surgeon, who popularised mastoid ecchymosis being associated with base of skull fractures in 1890 1. He was, however, not the first to note this association. Sir Prescott G Hewett (1812–1891), an English surgeon, had written a description of this very association previously 2.