The original novel which the film is based upon is set in a fictional town called 'Royale-Les-Eaux' (or 'Royal Waters' in English) Obviously a lot of the plot is based around a casino, hence 'Casino Royale' (a casino within the town of Royale)

Hi Grace, nice to meet you! Royal is an adjetive like "Real". It refers that the Casino is the greatest! I hope I´ve helped you!

It just means 'royal', it's a French word!

I think it's the french word for royal