I became confused by comments to my answer insisting that Technical writing is jargon using incorrect English words.

I also looked through definitions of "prepend" in internet, all with inserted derogatory remarks, even in IT-specialized dictionaries, like 'jargon' and:

• prepend is not an English word. It was created to sound like the opposite of "append," which means to add to the end. The correct English word is "prefix;
• Although it sounds correct, prepend is not an English word. It was created to sound like the opposite of "append," which means to add to the end. The correct English word is "prefix;" for example,

Is Technical Writing jargon or writing-style and the branch of correctly used English?
Would I better avoid to refer to it as English at all while copywriting (or copylefting) in it?

Update:
If I write using the words which are not English WORDS, do I write in English?

Update2:

I've read many definitions of copywriting but basically it is to poularize a product or a point of view to a most general (including illiterate) reader. The term Copywriting "refers to writing in the sense of creating non-technical material". Where is here a "jargon is nearly impossible for the average person to decipher", given by all answers, I wonder?

Update3:
Some of jargon definitions:

• Jargon (JAR´gen) - Meaningless use of words
• The technical language of a particular group that is inappropriate in most formal writing since it is frequently not understandable by those outside the group

What is unclear in "prepend" and to whom?
Why isn't busyness letter or step-by-step instructions a formal writing?

Update4:
Jargon is not necessarily incorrect words. I can speak a few jargons with completely correct words engagement which will be clear only to representatives of certain groups. It is the matter of enagaging accent, distinctiveness, allusions, metaphors, rare citations or facts and idioms

Should it be be understood that insulting obscenities known to everybody are not jargon and full members of "correct" English printed in all dictionaries, exposable in printed books, screened popular movies? but understandable "technical" ubiquitous words are out?

Jargon, when referring to computers, is the usage of words by a particular group, profession, or culture, especially when the words and phrases are not understood or used by other people. For instance, words like Adware and Spyware are considered Jargon. Many computer related acronyms, such as CPU (another name for computer processor) and RAM (another name for memory), are also considered Jargon terms

Do you know anybody who:

• who does NOT know the words RAM or CPU?
• who knows, without consulting with dictionaries, all "correct" words of a language?

Related question:

• Does English have taboo-ed (unprintable) obscenities? [closed]