顧炎武
The third character "fǎn" "turn back" is the usual marker of a "fanqie" spelling in the "Qieyun". In later dictionaries such as the "Guangyun", the marker character is "qiè" "run together". (The commonly-cited reading "cut" seems to be modern.) The Qing scholar Gu Yanwu suggested that "fǎn", which also meant "overthrow", was avoided after the devastating rebellions during the middle of the Tang dynasty. The origin of both terms is obscure.