Is there a word for a pair of words that would appear to be antonyms from their construction, but actually have the same or similar meanings?
For example, brief / debrief. From The Guardian:
A spokeswoman for the European commission said Barnier would debrief ambassadors and MEPs on the European parliament’s Brexit steering group.
The meaning wouldn't change much if it instead said:
A spokeswoman for the European commission said Barnier would brief ambassadors and MEPs on the European parliament’s Brexit steering group.
One can debate on a subtle change of meaning and as to whether the second use is actually correct (some dictionaries state that the verb brief means to inform ones superiors specifically), but we can probably agree that debrief is not, in this context, the antonym of brief, despite the prefix de- usually indicating a reversal (such as in decode, decompress, demystify, detoxicate).
Another example may be flammable and inflammable. The prefix in- often indicates a reversal (incredible, invisible, inalienable), but inflammable is rather a stronger version of flammable (intoxicate is not an antonym of toxicate, but doesn't have a similar meaning either).
Is there a word for the situation where two words would appear to be antonyms but aren't? I was thinking of auto-antonym, but that is a single word having two opposite meanings. Here, we have two seemingly opposite words having (almost) the same meaning, which is related but not quite the same.
