If someone doesn’t care one iota, they don’t care very much.
Like the letter “i” in English, an iota is the ninth and smallest letter of the Greek alphabet, and because the English letters “I” and “J” were often confused, iota became jot, with both words meaning something very small.
That’s why to “jot something down” means to condense information, while an iota is just a little bit more than a tittle, which is the dot over the “i.”
