separately vs under one's own steam

separately

adv
  • In a separate manner; not together; apart. 

under one's own steam

prep
  • At one's own initiative; of one's own accord, unbidden, unprompted. 

  • Using one's own resources; independently, unaided. 

  • Of the movement of a locomotive or a watercraft: by means of the power of its own engines (originally steam engines), rather than pulled or pushed by another vehicle. 

How often have the words separately and under one's own steam occurred in a corpus of books? (source: Google Ngram Viewer )