You might not care one iota about size, but we live with small things every day. For instance, an iota is the smallest letter in the Greek alphabet. Maybe you have wondered why Yoda, in the movies was so small. A Yodh or Yodr is the smallest letter in the Hebrew and Aramaic alphabets.
The phrase 'not one jot or tittle' comes from the 15th century bible translation. A tittle is the small mark above the letters i and j. Tittles have been around since the 11th century Latin manuscripts to distinguish those letters from the ones next to them and making reading text easier. The Irish may tipple, but do not bother with small things like tittles and do not use them for their letter i. A jot is the name of the least letter of an alphabet or the smallest part of a piece of writing. So, jots and tittles are small things. We have a thought and jot it down. We dot an i, but Chaucer would have tittled his. Size matters and small is important.