orangutan vs ourang-outan

orangutan

noun
  • Any of three species of arboreal anthropoid ape, characterised by their shaggy reddish-brown coat and long arms, which comprise the genus Pongo; Pongo pygmaeus of Borneo, Pongo abelii of Sumatra or Pongo tapanuliensis of South Tapanuli (in Sumatra). 

ourang-outan

How often have the words orangutan and ourang-outan occurred in a corpus of books? (source: Google Ngram Viewer )