Gratis comes from the Latin word for "favor;" so in English a party favor is a small item given gratis to everyone attending a party. Gratis is used as both an adjective ("The drinks were gratis") and an adverb ("Drinks were served gratis"). But however it's used, it means "free".

Is gratis a Dutch word?

The word 'gratis' (for free) is believed to originate from medieval times. It was part of a spell used by wizards and witches to entice people to part with their money. Today, the word continues to exert a magical influence over the Dutch. Just this week, I watched a Dutch breakfast TV show vandaag de dag.

Is gratis a common word?

Both are English words. Free is much more common. Gratis is a synonym for free. You can find examples in the Oxford Dictionary here.