HP vs hire purchase

HP

noun

  • Hit points; health points. 

name

  • The Hewlett-Packard Company 

  • Harry Potter 

hire purchase

noun

  • A method of purchasing an item, where the buyer hires it and takes possession of it and pays regular installments. Ownership is only transferred on payment of the final amount. Abbreviated as HP. 

How often have the words HP and hire purchase occurred in a corpus of books? (source: Google Ngram Viewer )