[ks2048]

I agree with this way of thinking about it, but the problem is “added to the lexicon” is ill-defined.

There is no official lexicon. When speaking English, the pronunciation of “Paris” has become well-established, but for countless other words, it has not.

[fsckboy]

linguists use the word lexicon (as opposed to dictionary) to mean those words which are spoken as prevalently, let's say, "as the syntax in which they are agreed and declined". (I just came up with that and think it's quite clever)

it has become over common to over point out that linguistics is descriptive, as if anything goes; anything does not go, and that is what linguists study. Stray from the lexicon, and people will ask what you are talking about. When they stop asking, it's in the lexicon.