Since these were both letters, the Japanese words used to describe them should have been contained the Japanese kanji 状 to indicate that they are letters. However, the Japanese kanji 帖, which means quire, was used since both of them were used as models for calligraphy.
書状ゆえ、本来は『風信状』・『久隔状』であるのを、「帖」をつけて呼んできたのは、法帖、あるいは書の手本とされてきたことを意味する。