The spelling of the word "Rumer" is quite simple once the pronunciation is understood. The word is pronounced as /ˈruːmər/ which means that the first sound is "r" followed by a long "oo" sound and then a short "uh" sound. The final sound is also "uh" followed by the "r" sound. Therefore, the spelling is based on this pronunciation, with the letter "r" appearing twice in the word to represent the two "r" sounds.