<http://www.oxforddictionaries.com/definition/english/overtone>:

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> `2.` (often overtones) A subtle or subsidiary quality, implication, or connotation:
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<http://www.oxforddictionaries.com/definition/english/undertone>:

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> `1.1.` An underlying quality or feeling:
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Are these meanings identical? What's the phenomenon or oddity called, where two words with opposite prefixes (not necessarily just over- vs under-) surprisingly mean alike? Would someone please explain the "paradox" here?