They derived from boilerplates (shosoku-shu) which were a collection of correspondence from the late Heian period written by those who were engaged in literary work, such as nobles (A similar item called "Tokarissei," reportedly from China, is preserved in Todai-ji Temple Shoso-in Treasure Repository, but even this had been arranged from the Chinese original, showing that oraimono developed independently with an influence from China).
平安時代後期より公家などの文筆に携わる人々が往復書簡（往来）の形式を採った文例集（消息集）に由来している（同じ様な形式のものは、中国伝来とされる『杜家立成』が東大寺正倉院に収められているが、当時の中国の書式を元により整理された形式となっており、往来物が中国のものの影響を受けながらも日本独自に発展していったことが分かる）。