"jargon of thieves and vagabonds," 1841, from German Rotwelsch, literally "Red Welsh," from rot (from PIE root *reudh- "red, ruddy") + Welsh because obscure and difficult. But the first element may be connected with Middle High German rot "beggar."
rotter
Rottweiler
rotund
rotunda
rotundity
Rotwelsch
roue
Rouen
rouge
rough
rough rider
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