I came across the word tantibus while reading this page (as part of a bigger word, amalgotantibus), where it's claimed to be Latin for "nightmare"; a little bit of digging also revealed that it's the basis for the name of a My Little Pony: Friendship Is Magic character. However, I cannot find this word in Wiktionary or any other online Latin dictionary that I know of (Numen: The Latin Lexicon is my usual go-to), and while googling the word does turn up a lot of results (over 150,000, last time I checked), many of which similarly claim the word is from Latin and means "nightmare", none of them are reliable sources of etymology (e.g. reputable dictionaries like Merriam-Webster, official scientific publications).
Is tantibus really a Latin word, or is this a made-up one (i.e. "neo/pseudo-Latin") that someone somewhere mistakenly believed to be real Classical Latin, and their mistake propagated over time?