look after vs watch out for

look after

verb
  • To follow with the eyes; to look in the direction of (someone or something departing). 

  • To care for; to keep safe. 

  • To seek out, to look for. 

  • To have as one's business; to manage, be responsible for. 

watch out for

How often have the words look after and watch out for occurred in a corpus of books? (source: Google Ngram Viewer )