tldr; - See: SO WHERE DID COPYPASTA COME FROM
Josh wrote a very interesting question about the origins of the term copypasta. I find it very intriguing as well. He did some excellent homework on the origins (see above in his original question posting).
It appears the word may have originated after being coined in use by 4chan's Anon community circa 2006.
I say may have because I'm still not convinced that it actually originated there; it may have but that's not entirely clear yet. However, let's just assume that's right. I would like to dive into how it may have come into existence (even if it did originate there - this is more about the "why" and "how").
Without even checking the link above it is obvious that copypasta is a portmanteau of "copy" and "pasta". However, why did users begin to coin this phrase? RaceYouAnytime makes a great answer post about some findings on the use of the word; but I find the answer to Josh's post less about the nature of whether it's derogatory or not and rather more about why and how it came into use.
First, some history. What does "pasta" have to do with anything? Well, back in the early days of computer programming many languages shared a feature known as a "goto" statement (which also required a label - you would "jump" to the label by saying "goto begin-loop", or some such thing. This created a mess of coding, especially if the coding was unplanned or ill implemented. By the mid 1980's or so we had a full fledged pejorative for this type of thing: Spaghetti Code. It's mentioned as early as 1977 at a symposium, but it was not until around 1979 that we had a published version of the word. However, references to "Spaghetti" type coding go all the way back to 1968 (or at the least the beginnings of problems with "goto" type programming).
Fast forward a few years, maybe even up to a decade or so, and we also have the rise of "copy/pasting". Technically it goes back to as early as 1975-1980 but it was not pervasive until the 1980's, even the later 80's.
THE INTERNET AND SPAM
By the mid 1990's the inernet and "web browsers" were catching on very quickly, email use began to proliferate, and SPAM had begun to be a serious issue. It gained a definite pejorative sense extremely quickly. I mention spam here not only because of it's reference in the OP's post but because the internet and tech culture has a long and storied history of using food and various other items to describe derisive and unwanted terms and/or to create portmanteaus.
SO WHERE DID COPYPASTA COME FROM, OR RATHER, WHY DID WE BEGIN USING IT?
I believe it began as a way to combine the pejorative's of "spaghetti code" (noodles or pasta) with the unwanted and intentional copying/pasting (or SPAM-like activity) into a portmanteau that embodies both concepts. It's a word the community came up with to describe a way of "noodling" or "jumbling" the content of sites by casually copy/pasting information all over the place.
The internet, and the rise of forums, social networks, memes (more about that in a moment), etc... gave way to a culture in which we create new words all the time. It makes sense too. In the last 40 years we have seen more innovation than the entirety of human history (which goes back, arguably, from 300k-500k years for "modern" homosapiens). We need these words. But internet subcultures, which up until roughly 10 years ago (best case), were composed of people who by their nature were curious, innovative, and looking for more compact ways to express ideas. This has always been the aim of the programming elite and various techy subcultures.
It's in this way that I think the word came to be. This was likely the communities way of saying, "stop copying/pasting things all over because its noodling up our site and adding no value [as it can be found elsewhere with a simple link]". I would imagine this was the case because it's likely that a subset of programmers or techies started the use of the word, especially as far back as 2004-2006, and I would imagine they were combining the concepts of spaghetti code (or pasta) and the idea of SPAMMING (which was being done by blatantly copy/pasting everywhere) to create the portmanteau: copypasta.
I think the mixing of the words, copy and pasta, into a portmanteau is very similar and analogous to how the phrase, spaghetti code, came into existence. It seems highly likely with the early internet culture's obsession with Monty Python skits, which were, at least partly, the fuel for the usage of food items (such as SPAM) to describe undesirable actions, that this is how we came upon, "copypasta". This would be my overall hypothesis.
EXAMPLES OF INTERNET OR TECH ORIENTED ITEMS RELATED TO FOOD
I'm not going to include an exhaustive list but there are some I can think of right away. I'll include items from this discussion as well for completeness:
- copypasta (obviously - the discussion of this post)
- Creepypasta (a similar type of word)
- Spaghetti Code (see links above)
- Ravioli Code (This is a term that came about much, much later with the growth of something known as "Pair Programming" and Agile practices. Basically what happened is software design went through a paradigm shift and programs went from something known as functional or structure top/down coding to a more "loosely-coupled, object based" design. This allowed for easier extensibility, maintainability, and efficiency. The term refers to the "bite size" pieces of Ravioli which are like the "methods" we use in object oriented programming today and refer to it's loose coupled nature.)
- SPAM (see links above)
- HTTP Cookies (web cookies)
- Magic Cookie (also likely the root/origin for modern internet cookies)
- Java (the programming language)
- Java Beans (another variation on the Java language)
- TechSoup (an organization started in 1987)
- The Droste Effect (a Dutch term for a specific type of recursive picture - recursion is a CS topic beyond the scope of this entry - but what is interesting about this is that "Droste" is a reference to Droste cacao and hot chocolate products)
- Apple Computers (founded late 1970's)
Again, there are others, this is just what I thought of right now.
And this last one I have set aside for special consideration:
- "Hash"tag (#). Everyone knows this today from Twitter but the concept of hashes and/or hash "marks" have been around forever (they go back to the very beginnings of Computer Science theory).
This is not conclusive at all (fair disclaimer) but it is another hypothesis of mine that the many, many decades long use of the word hash, hash tables, hashing, hash trees, hash graphs, hash functions, hash maps, hash keys, etc... could have ultimately come from the food item "Hash" (a meat dish chopped up in bits in various configurations depending on locale).
In fact the interesting thing is that if you look at a hash mark (the common "pound" sign - another indication it may have roots in food), #, it resembles, potentially, a dish that has been cut up into pieces for serving. This is just something I find very interesting but I would need to do more research to give it a fair level of confidence.
And it's not just foods either. I could fill pages with the various acronyms, portmanteaus, compound type word structures or phrasings, etc... that have been created in various tech subcultures throughout the decades. One's which either have a certain assonance, onomatopoeia, or metaphorical ring/tone. It's literally endless as far as that goes. Interesting stuff :)
I said I would mention meme's and I want to just briefly mention it because it's amazing to me how this word became so popularly used today. It doesn't necessarily relate exactly to the question but it's tangentially important to understanding this overall concept. Meme was a scientific word. It was a word that anthropologists and social biologists used to describe social viral concepts. "Meme", as it is used today is another example of how the true meaning of a word can change, how internet culture can affect its purpose, and even radically change the intention.
Meme as used today, by most younger people, just means a picture/GIF with some very catchy, funny, phrasing on it - usually one that has had viral success. That is how that word mutated to what it is today. As opposed to it's original intent which was rooted in anthropological and biological studies to understand how ideas/concepts are shared among a culture, and passed from generation to generation, like a "virus". I think it's an important and great example of how we see words come into being, change meaning, or, at least change meaning within certain contexts (the meaning has not totally been lost in this case). I would like younger readers to understand that "meme", and how it relates to "viral", are so very close in meaning and relation to each other but they did not actually describe the same process originally. The concept of something "going viral" is almost directly borrowed from "meme". But a "meme" to most young people is a thing that has become viral (not the mechanism by which social viruses are transmitted - which is closer to it's original scientific purpose). I guess we could say that the GIF (or now even YouTube videos) is the memetic mechanism for information exchange and viral phenomenon. But most young people don't understand that interpretation. It's a brave new world :) We live in a constantly evolving soup of words and euphemisms :)