jot or tittle

The slightest change. In the King James version of Matthew 5:18 we read, “For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.” A “jot” was an iota, a very small quantity (we still use the expression “not one iota of truth”); a tittle was a tiny accent mark. Accordingly, to have said “not one jot or tittle” was a very erudite way of refusing to make even the most minor alteration.