Answer:
Mercury is Hermes.
The god of travelers, doctors, merchants, and anyone who uses the road.
He is also the god of theives.... (Watch out!!!!)
Mercury gives us the name for the liquid metal used in thermometers, and can be a synonymn for heat ("the mercury is rising" = it's getting hotter) and also the adjective mercurial. Hermes gives us the adjective "hermetic" (cf. 'hermetically sealed').
PS -- The Romans "Romanized" the Greek religion by associating one of their gods with each god of Greek culture. Eventually, the traditional Roman god lost his identity, and the two names became completely synonymous: Mercury = Hermes; Mars = Ares; Jupiter = Zeus; Bacchus = Dionysis. (Theoretically, this can also happen with mortal figures, but the only example I can think of is the Homeric figure Ulysses = Odysseus.)
In our own, monotheistic civilization, we do not have names for god, but the word God itself takes different forms in different languages, for example Dieu for French speakers, Gott for German speakers, Bog for Russian speakers, Allah for Arabic speakers (whether Moslem or Christian or Jewish). But these all are just literal translations of the word God. "There is no God but Allah" is thus a mistranslation. The sentence really says "There is no God but God" and is an affirmation of a belief in a single God. It is the equivalent of the Hebrew "Shma": "the Lord our God the Lord is one" and the First of the Ten Commandments: "I am the Lord thy God... Thou shalt have no other God before me."
We often refer to God not directly but with descriptive names such as "The Lord" or "The Creator"; the ancients also had multiple epithets for each of their gods.