A traditional Japanese emblem used to identify a family, often seen on formal kimono, gravestones, and historical artifacts.
His kimono had a family crest on it.
お墓に家紋が刻まれている。
The family crest is engraved on the gravestone.
Compound of 家 (ie, 'family') and 紋 (mon, 'crest' or 'pattern'). The term has been used since the Heian period to denote hereditary family emblems.