Zuihitsu derives from the Kanji for “at will” and “pen.” There is a whiff of whimsy in this that I really appreciate. Writing for no real reason, just because one feels compelled. They’re spontaneous, confessional. There is no format or structure, which I guess makes the lack of structure the format?
Most well-known writings in this genre-defining genre that I’m aware of: The Pillow Book by Sei Shōnagon (poet and court lady, Heian period), Essays in Idleness by Yoshida no Kenkō (whose title has also been interpreted as The Harvest of Leisure), Hōjōki by Kamo no Chomei (translated as The Ten Foot Square Hut or My Account of My Hut).
I’ve read the last two. Essays in Idleness is written in the form of small micro essays, all numbered, and the entries range from self-deprecation (ruminating on how stupid it is to be sitting there writing at all) to court gossip and contemplating on Buddhist philosophy. Hōjōki is a long, meandering essay on life in (you’ll never guess!) a hut. Both were involved in the court in some capacity before becoming monks and hermits. Chomei abandoned city life after being employeed as a court poet, while Kenkō was an officer of the guards in the Imperial palace in his former life.
“What a strange, demented feeling it gives me when I realise I have spent whole days before this inkstone, with nothing better to do, jotting down at random whatever nonsensical thoughts that have entered my head” —Kenkō