As with any endeavor in life, it is usually best to learn the rules before breaking them.
Prepend arose because append began to mean add to the end rather than merely add in common usage. It would have been correct to say append to the front of the list, but it is increasingly likely that some people would find it confusing. Not to mention that it takes more keystrokes or syllables to do the job "properly" and we all operate on the Principle of Least Effort (that is to say, we're fundamentally lazy).
New word coinages happen all of the time. Some new words become vogue words for a while and quickly fall out of general use. some are useful enough to become part of a group's jargon, but never see any use outside of a specific field. Some are co-opted from jargon into general use. Others just make so much sense (their meaning is obvious and they neatly package a concept that is otherwise difficult to express) that they almost immediately become part of the standard language.
None of this means that you can take a word that has a precise meaning in one context and spring it on the general public with the expectation that they will have any idea what you're saying. If you use a technical term, for instance, it might not help that there are resources that define the term perfectly -- if people don't understand the terms used in the definition, they still won't know what you're talking about. The same thing goes for new coinages. If you make up a word, there's a chance that people won't know what you mean -- but there's also a chance that the meaning is perfectly clear and obvious. (Shakespeare did quite a lot of that, sometimes very successfully, sometimes not.)
One thing to keep in mind is that it's horribly impolite to go breaking into someone else's property and declaring yourself to be in charge. The Humpty Dumpty approach rarely works.