How to translate "雲兒" into English?
兒
  
  http://www.cantonese.sheik.co.uk/dictionary/characters/90/
  
  [4] final particle / suffix, placed after many commonly used nouns to avoid employing one-syllable terms in speech (very common in the Beijing dialect 北京話, see: 兒化, 兒化韻)


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  "藍天高高雲兒飄飄" --> "High, high blue sky, little cloud float around"


The dictionary only mentioned 兒 can be used as a suffix, placed after many commonly used nouns to avoid employing one-syllable terms in speech.

In my opinion, adding the 兒 suffix to an object, can also humanize the object. For example, calling a goat '羊兒' or '羊羊' instead of '羊' give it a hint of youthful, human character. (like in typical baby talk)