weeb
The word weeaboo first appears as a nonsense word in a 2005 Perry Bible Fellowship webcomic: https://pbfcomics.com/comics/weeaboo/
It gained its current meaning later that year. On anonymous web forum 4chan, “wapanese” was then a common slur used against white people who enjoyed anime and manga. As an intervention, moderators added a word filter that replaced all instances of it with a ridiculous word that didn’t mean anything, “weeaboo”. This did not dramatically reduce the frequency of its usage, but it did end up changing the word that was used.
Weeaboo continued to be a common enough word on the internet that a short form, weeb, became standard within a few more years. It has mostly lost its original pejorative sense.
hello
The greeting hello is first found in print (spelled “hulloa”) in a 1878 Connecticut phone directory. Before becoming the default English phone greeting word, it was used in the American West as a nonsense shout to get attention, as early as 1826. It’s likely related to similar attention-getting English shouts, probably descending from “Hey! Lo!” over a thousand years ago.
Notably, Alexander Graham Bell preferred the use of a different specialist greeting word, the nautical ahoy, when answering the phone. His reasoning was similar to “hello” - it was an existing word that wasn’t widely used and was easy to distinguish from any other word, like how Alexa or Siri were decided on as wakewords more recently. In a recurring theme, “hello” had Edison’s support and eventually won out, although the deciding factor was probably early phone etiquette guides recommending its use. Bell continued to answer the phone with “ahoy” until his death.
You may notice just how path-dependent this development is. In particular, early phone etiquette developing differently in different countries can be a fun mirror into alternate realities. For example, Mexican Spanish uses ¿Bueno? as shorthand for “Is the connection good?” while Spain Spanish uses ¿Diga? meaning “Yes, speak?”
werewolf
The word werewolf predates English, which means it was first used some time before the year 400. It’s a compound of wer-, meaning “male person”, and -wolf, meaning “wolf”. Basically just “Man-Wolf” (1962, DC Comics) or “The Wolf Man” (1941, Universal Pictures), except using what was then the word for “man”.
Notably, wer used to be the English word for “husband” before husband took over its meaning around 1300, a revelation if, like me, you ever wondered why it looks so different from “wife”. A married couple were wer and wyf before then. The Latin equivalent is vir-, like in virile.
Today, were- is a productive prefix in English, yielding gems like weretiger, which can be used without any consideration to the weretiger’s gender.
nerdsnipe
The term nerdsnipe originates from a 2007 xkcd webcomic, perhaps inspired by a real-life anecdote from John Conway, the inventor of Conway’s Game of Life. As with all xkcd webcomics, additional background information can be found at its associated explainxkcd article: https://www.explainxkcd.com/wiki/index.php/356:_Nerd_Sniping
One thing I appreciate about the term is that it’s a microcosm of how English compound words are created. In the originating comic it’s spelled “nerd snipe”. Three years later, the same author spells it “nerd-snipe”. I don’t have a good date on the unhyphenated version, but I can see that I was using the spelling “nerdsnipe” by at least 2018. One interesting point of comparison is when news outlets and style guides started dropping the hyphen in “email”, and extrapolating that most people probably started dropping it a few years before that.
okay
Doing silly things with language transcends time. Today we say smol and chonky, while in 1830s NYC there was a thing around misspelled abbreviations, like K.Y. for “no use” (know yuse) and N.C. for “enough said” (nuff ced). One that got popularized in 1839 was O.K. for “all correct” (oll korrect), which gradually rose to national prominence through use in a presidential campaign and the need for a quick way to write “looks good” on the gradually increasing volume of paperwork.
In 1929 - ninety years later! - the alternative spelling okay began displacing the original initialism. Quite some time after that, okay was such a common word that it got abbreviated again to k in text messages.