Пешком

In Russian, the word for “foot” is нога (which is also the word for “leg”). But if you go somewhere on foot, the adverb you are looking for is пешком, which bears no resemblance to нога. In Portuguese, there is pé “foot” and a pé “on foot”; in French, pied and à pied; in Greek, πόδι and με τα πόδια.

As it turns out, пешком was derived from пеший “pedestrian”, which is derived from the same root as Latin pes, English foot, Ancient Greek πούς. Also related is the word пехота “infantry”.

But нога is actually related to Latin unguis (Portuguese unha was derived from the diminutive ungula), English nail, Ancient Greek ὄνυξ, which makes it all the more amusing to hear people say лапа to mean “hand” or “leg”.