Where do new words come from and how do they get into the dictionary?
New words arise constantly through a handful of recognised processes, and dictionaries record them long after ordinary people started using them.
How words are formed:
Borrowing from other languages — English has absorbed enormous numbers, from tsunami to algorithm.
Compounding — joining existing words: smartphone, paywall.
Blending (portmanteau) — merging parts: brunch, podcast, emoticon.
Derivation — adding affixes: unfriend, hyperlocal.
Conversion — shifting word class without changing form, as when the noun google became a verb.
Clipping — shortening: app, fridge.
Acronyms becoming words — laser, scuba, both originally initialisms.
Eponyms from names: sandwich, boycott.
Semantic shift — an existing word acquiring a new sense, which is how mouse, stream, cloud and viral all changed.
Coinage from nothing is genuinely rare.
How a word enters a dictionary. Lexicographers do not approve words; they record them. Modern dictionaries work from vast databases of real usage called corpora, monitoring how often a word appears, across how many different sources and contexts, and over how long.
The criteria are roughly: widespread use across varied sources; sustained use over a period, typically several years; and use without explanation, meaning writers no longer feel the need to define it. That last one is the strongest signal that a word has arrived.
Two common misconceptions:
There is no authority. English has no equivalent of the Académie Française. Dictionaries compete and disagree, and inclusion in one is not official status.
Being "in the dictionary" confers nothing. A word is real when people use it and are understood. Slang, jargon and regional terms are real words whether recorded or not.
Words also leave, marked obsolete or archaic.