Ha, I knew that! Two quite basic Greek words! Especially ποταμός appears quite frequently! This "fact" isn't actually quite correct, though: the word for horse is ἵππος, not ἵππο! Words can never end at ο in Greek, so in fact it should be kind of obvious. The word ἱπποπόταμος actually also exists as one word in Greek, as they already knew about the animals.
We've seen more trains than Lumia phones on this thread (thanks to Tom and me ) Here's a tram for a change