How do you trademark a word that you made up?

The requirements to register a trademark are:

That the mark be used to describe a service, product, business. That it be used as a brand.

That the item being named by the trademark is in business or currently available to purchase. That is, that it is currently used “in trade”.

Register trademark in Vietnam

That your application describe the product or business sufficiently that the trademark office can assign it to a specific class of business (e.g. apparel). Trademarks only limit use by other businesses within that class of business. Apple Plumbing does not have to worry about being sued by Apple, who are in the class of electronic goods and computer software (among others).

I suspect what you are really trying to do is prevent anyone else from using this word that you made up. A word that has a specific definition in English and an intended use when communicating.

Trademark (and copyright, for that matter) are not at all interested in limiting the ability of people to communicate. Words, names, punctuation, symbols/letters/numbers are all without protection, free for anyone to use in normal communication. The trademark of “Apple” clearly doesn’t prohibit me from discussing the fruit that makes a delicious pie or strudel. It only prohibits me from using it to describe my own product or business which competes with Apple’s existing products or business.