It originally meant poems and personal notes and letters of the Chinese classics addressed to a wide variety of people including family members and friends to exchange personal feelings, but in "Manyoshu", poetry about love between men and women was categorized as Somon.
元は漢籍の書翰などで家族・友人など広い範囲の人々を対象とした私情を交わす書翰や歌に対して用いられてきたが、『万葉集』では転じて男女間の恋愛を詠った作品をまとめて呼称した。