declare vs swear to

declare

verb
  • To make outstanding debts, e.g. taxes, payable. 

  • To show one's cards in order to score. 

  • To explicitly establish the existence of (a variable, function, etc.) without necessarily describing its content. 

  • For a constituency in an election to officially announce the result 

  • To assert or announce formally, officially, explicitly, or emphatically. 

  • For the captain of the batting side to announce the innings complete even though all batsmen have not been dismissed. 

  • To inform government customs or taxation officials of goods one is importing or of income, expenses, or other circumstances affecting one's taxes. 

swear to

How often have the words declare and swear to occurred in a corpus of books? (source: Google Ngram Viewer )