1
general::
Phrase(s): not one iota
not even a tiny bit. • I won’t give you any at all! Not one iota! • I did not get one iota of encouragement from any of those people.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Not even the smallest amount, as in He got not one iota of thanks for his efforts. This usage appeared in slightly different form in the New Testament (Matthew 5:18): "One jot [iota] . . . shall in no wise pass from the law till all be fulfilled." (The noun jot comes from the Greek iota.)
American Heritage Idioms