retrench on vs update

retrench on

update

noun
  • A version of something which is newer than other versions. 

  • A modification of something to a more recent, up-to-date version; (in software) a minor upgrade. 

  • An additional piece of information. An addition to existing information. 

  • A change in information, a modification of existing or known data. 

  • An advisement providing more up-to-date information than currently known. 

verb
  • To bring (a person) up to date: to inform (a person) about recent developments. 

  • To bring (a thing) up to date. 

How often have the words retrench on and update occurred in a corpus of books? (source: Google Ngram Viewer )