Every year, lexicographers--people who write dictionaries--have to delete words from newer editions of dictionaries. How do they decide which words to eliminate? Jen Doll of The Atlantic explains:
To determine which words are most relevant today, editors comb through a variety of sources (Google Books, LexisNexis, other dictionaries, the entire Internet). A word that’s still widely read—a thee or a thou—should stay, even if it’s not used by contemporary English speakers. To survive in the Collegiate Dictionary, Stamper says, a defunct word must appear in books that the average high-school or college student is aware of. So an archaic word found in Shakespeare or Milton gets a reprieve, but one favored by Samuel Pepys or Anthony Trollope may not. [...]
As for those words now facing an unhappy fate—landlubberliness!—preservationist types should use them whenever possible. Take the case of snollygoster, a noun meaning “an unprincipled but shrewd person,” which was removed from Merriam-Webster’s Collegiate Dictionary in 2003. When news got around that it had been dropped, Stamper says, people took up its banner: “We have, oddly enough, seen more unironic and unself-conscious use of snollygoster in print in the last few years.” Principled or not, the ploy has been shrewd. Stamper says that if the word really takes off, Merriam-Webster will “certainly consider adding it back.” Perhaps it only takes a crowd of snollygosters to save a snollygoster.
It would be tragic if a word as fine as snollygoster would be extinguished. I'll start using it.