"epicaricacy" fails the simplest test for word-ness: it's never [0] used with the expectation of being understood without explanation. (Nor ever has been, according to Wiktionary.) It seems to have been one of the earliest Nihilartikels.

It could still be adopted as a learnèd (read: pretentious) borrowing from Greek, of course, but in that case it would be spelled epicharicacy.

[0] Edit: Well, hardly ever. https://en.wiktionary.org/wiki/Citations:epicaricacy#English