Learn English – “Pending” vs “Impending”. Are they synonyms

The New Oxford American Dictionary has the following note.

For complex historical reasons, prove developed two past participles: proved and proven. Both are correct and can be used more or less interchangeably: this hasn't been proved yet; this hasn't been proven yet. Proven is the more common form when used as an adjective before the noun it modifies: a proven talent (not a proved talent). Otherwise, the choice between proved and proven is not a matter of correctness, but usually of sound and rhythm—and often, consequently, a matter of familiarity, as in the legal idiom innocent until proven guilty.

How about false enemies?

I originally voted to close because I thought synonym was an adequate generic term here, but Stephen's comment re false friends prompted me to Google language "false enemies". It seems clear that this coinage has occurred to others (here it is in a Wikipedia talk page, for example).

The first other "clear-cut" example I came up with was ravel / unravel, but I've found a couple more since, as have others here - maybe OP's right, we need a word to Know thine enemy!

EDIT: If an out-and-out neologism is acceptable, there's always the crypto- prefix (secret, hidden, or concealed), so they could be cryptosynonyms (though I must admit that one doesn't yet seem to have occurred to anyone else within the scope of Google's indexing routines).