University student, beginning to learn about corpora, developing a research question for an assignment. There may well be linguistic concepts and terminology that already cover this idea and that I am not aware of. I would appreciate any knowledge about this that you can give me.
My idea is to use diachronic corpora to try to determine a usage threshold, or point of no return, below which words typically do not survive in a language.
An example: Pronominal adverbs in English are mostly used as techinical jargon (e.g. herinafter), archaic (hereunto) or part of everyday English (therefore). I analyzed these types of words in NGRAM viewer and noticed that, since the 1560s "therefore" has never fallen below the 1/100ths usage percent and hereunto has never risen above the 1/1,00ths. I'm aware NGRAM may not be the best corpus for this.
Have any studies been published that suggest a usage amount that typically determines if a word will become archaic, or obsolete?