So I've been doing a good bit of snooping around reddits and writing forums and I've come across the seemingly widespread opinion that using made-up words in fantasy can easily kill your book. I've even seen a number of people say that seeing one on the first page is enough to make them close the book.
I understand that using made-up words is often used as a poor attempt to add worldbuilding to a story without developing it properly. A lot of times authors will just replace a word with a fabricated one for no purpose besides trying to introduce a different culture, but it has the same effect of talking about a character without letting the audience see their character in action. However, when is it acceptable to use a made-up word? If there's proper reasoning for the word to diverge from the common word we use for it now, is that acceptable, or should a writer just continue to use the common word? And does the general stigmatism toward made-up words only cover entirely fabricated words (such as, for example, ellenfenim or something being a word for a specific grain) or does it also apply to combinations of modern words being used to describe something different (example, goldgleam describing a particular kind of light from a unique light source). I feel like the aversion to made-up words can discourage some of the more fantastical elements of the fantasy genre, such as inventing things and breeds that don't exist in the real world, or is it acceptable to use these words then?
I wanted to ask this question because one of the stories I'm currently writing utilizes a couple of fabricated words, and I wanted to ask whether or not they were acceptable.
There are only two completely fabricated words: ilis and vioz, both of which refer to a grouping of 6 castes that are present throughout the world and replace the world family. For example, a member of the 4th Caste belongs to the (family name) ilis, and may be referred to as an ilis. Same goes with vioz, but for the other 6 castes.
I also used several combinations of words to describe unique concepts. Examples are coldglow, which refers to specific light given off from a type of fog known colloquially as the Cold, coldforged which stems from weapons forged using the fog, and nightwater, which references a type of poisonous water that has the appearance of a night sky, black studded with stars.
My inquiry is; are these usages acceptable, and why or why not? Are they too much? Where is the general line for using fabricated words?