Why not start off with a digression?
The other day I overheard someone (X) say something like:
"I lied, but not on purpose."
This is a great example of how lie is changing its meaning to have less force. At its core, to lie means to say something untrue. There are various ways that we can say something untrue, for example when we joke. However, in the past when a person was described as lying, it meant that they said something untrue with the intent to deceive. However, X clearly did not intend to deceive, and indicated that explicitly.
We can paraphrase X by "I said something untrue, but without any intent to deceive". The phrase "but not on purpose" is cancelling the presupposition that lying involves intentional deception. In other words, lie has been weakened by having intentional deception demoted from part of the inherent meaning to a presupposition.
This change has been going on for quite awhile. I first came across it when teaching a basic semantics class. After explaining the difference between inherent meaning and presupposition, I set up the simplistic scenario where people in 1491 did not know that the Earth is round. I then asked the class whether a person in 1491 who said "The Earth is flat" could be described as lying. While I was confident that the answer was negative (they would be described as mistaken), a good portion of the class answered affirmatively. I was shocked. Further probing showed that the class did understand the notion of presupposition and simply had a different meaning for lie
How did lie come to change its meaning? I have an unsubstantiated guess. There was/is a kind of interaction where a person would realize they made a mistake, and jokingly say something like, "Oops! I lied." With enough usage, the joking aspect disappeared for many people, and the meaning of lie has weakened to the presuppositional one.
However, even though I understand X's use of lie and how we got there, I'm still taken aback by it.