Where does “rookvrij” come from?

rookvrij (Dutch) comes from Dutch rook, from Middle Dutch rôoc, from Old Dutch rōk, from Proto-Germanic raukiz, from Proto-Indo-European rewǵ-, from Proto-Indo-European rew- — to roar, growl, grumble; to roar; growl; grumble;...

rookvrij (Dutch): smoke-free, non-smoking