The formal name is koban, which was clearly mentioned in "Sankazue" (Picture Collection of Three Coins: History of Coinage in Japan), however, ancient coin books including "Kinginzuroku" (Gold & Silver catalog) and "Dainihon Kaheishi" (Great history of Japanese coins) called it kobankin.
公式な呼称は小判であり『三貨図彙』では「小判」と明記されているが、『金銀図録』および『大日本貨幣史』などの古銭書には小判金（こばんきん）という名称で収録されている。