Just how many times does a word need to be used, to make it legit!You'd have to ask one of those harmless drudges (a lexicographer). The "problem" with
epicaricacy is that it seems to have shown up in a dictionary (a later, posthumous, edition of Bailey's) before it ever made it into print. (At least, nobody has been able to cite its use before it showed up in a dictionary.) Of course, once something makes it into the dictionary (cf.
dord), it's fair game for adoption. This word's champions insist that it is an English alternative to the German
schadenfreude, when in fact
epicaricacy is a loanword from Greek. Plato, in his
Nicomachean Ethics, is the first person to use it or its Greek equivalent ἐπιχαιρεκακία (
epikhairekakia).
Schadenfreude, on the other hand, was coined in German (in a translation of Seneca and about a thousand years later). It's pretty much a word at this point. It's just that not many people know about it, use it, or care. As opposed to other synonyms, it does have much to suggest itself for use over its cousin. They pretty much mean the same thing. Go ahead and use it if you want to or must, but I'll stick with
schadenfreude, which has the advantage of not needing footnotes when you use it.