There are several theories about the naming process of Hidaka City; however, it was made by combining the initials of Mt. Hiwada and Koma County and it has no relation with Hidaka Province of the southern part of Hokkaido (or the origin of the provincial name, Hitakami Province); The origin of the name of Aki City in Kochi Prefecture lies in Aki County, Tosa Province (Kochi Prefecture) and it has no relation with Aki Province in the western part of Hiroshima Prefecture.
埼玉県の日高市は諸説有るが日和田山と高麗郡の頭文字を取ったもので北海道南部の日高国（或いは、その国名の由来となった日高見国）とは関係せず、高知県の安芸市は土佐国安芸郡(高知県)が由来であり広島県西部の安芸国とは関係しない。