Synantonyms...?

Once upon a time, there was a conversation. One person pontificated, somewhat ironically, that she was a taker, not a giver. She attempted to clarify her statement by saying that her sister was a caregiver, and she a caretaker. Hilarity ensued, as hilarity is wont to do.

Time passed, as time is also wont to do.

There was then another conversation, wherein this tale was told to the purveyor of a certain blog, and all present recognized the blogworthiness of the anecdote.

Brains were racked for any other example of a pair of antonyms (giver-taker) which, by the addition of a prefix, suffix, or compounding word (care), became a pair of synonyms. The best pair that could be found was "sinkhole" and "swimming hole", which are not actually synonyms, but certainly are much more similar than "sink" and "swim."

And so we ask you, o faithful readers, our muses, we beseech thee tell us, is this an example of a class of words, either of antonyms or of synonymizing augmenters, or is this a random linguistic accident of the sort produced by thousands of monkeys with thousands of typewriters?

Thanks to Tali for the idea, and for your forbearance as we take artistic liberties with the tale.