I don't recall anyone ever mentioning anything about any gods anywhere, but clearly the people in the Star Wars -verse believe in a higher being demonstrated with the Vice-Admiral's "God be with you" as a final farewell and good luck.
The idea of gods certainly exists in the Galaxy far far away, there are several examples of people worshipping gods or making reference to gods. The Jedi in The Last Jedi are referred to as "a religion" however in lieu of a deity they worship The Force.
Examples of gods or deities in canon include:
- C-3PO being worshipped as a god by the Ewoks in The Return of the Jedi
- The Gungans are known to have a pantheon of gods with preists that have significant possibility to gain power.
- In Episode 12 of Season 1 of The Clone Wars TV show, Dooku refers to Florrum as a "godforsaken planet".
- On Mortis "incredibly powerful" force-wielders are referenced to be god-like, from the 15th, 16th and 17th Episodes of Season 3 of The Clone Wars
and were drawn into a paradise realm inhabited by unspeakably powerful Force-wielders. These god-like beings were locked in an eternal struggle for dominance, which made Mortis the fulcrum of the entire galaxy and the Force.
Mortis - Star Wars Data Bank
- In companion books to the Force Awakens, the Church of the Force (most prominently seen when Lor San Tekka's village of worshippers is destroyed in The Force Awakens) believe in the requirement of the return of the Jedi to restore balance to The Force. A similar but opposite worship is the Acolytes of the Beyond who worship the Dark side of the Force. They however only exist in written canon.
For more examples of the appearances of deities a complete/near-complete list can be found here under the appearances tab
The movies all take "along time ago in a galaxy far, far away".
It's never been explained how the human race arrived in this galaxy, or how "Basic" (actually English) became such a common language. Many canon books reference a "belief" that humans originate on Coruscant, but it's far from certain.
One of my favorite theories is that the Earth galaxy eventually becomes uninhabitable, and the only other "habitable" galaxy they can find is one in the past. They travel there, (maybe settle on Coruscant), and evolve along with other species in the Star Wars galaxy.
ACTUAL ANSWER: with this backstory, it's easy to imagine "God" evolving as part of the English ("Basic") language. The people saying "God be with you", "Godforsaken", or "thank God" may not actually know what they're saying.