Antipodes: directly opposite.

Once used in the United Kingdom to refer to Australia and New Zealand.  After all, those countries are on the opposite sides of the globe.  This means, of course, that the feet of the residents of those countries are directly opposite. 

Thus, the source of the word.  The Greek word ἀντίποδες (antipodes), comes from ἀντί (anti), opposite and πόδες (podes), which is the plural of πούς (pous), foot.

Figuratively, we can use the word to describe something which is the exact opposite.  For example, the Democrats are the antipodes of the Republicans. 

Of course, anyone who believes that needs to schedule an MRI. 

Fool me once, shame on you.  Fool me twice, shame on me.  Fool me three times, I am a Republican!