past historic tense vs present imperfect

past historic tense

noun
  • A tense used in some languages (such as French and Italian) in narrative, and in spoken language primarily when reading narrative or in storytelling, for completed actions in the past or in speaking of the dead. It is semantically the same as the simple past in many languages, including English. 

present imperfect

noun
  • A grammatical tense which presents the action in the present as continuous, not yet over 

How often have the words past historic tense and present imperfect occurred in a corpus of books? (source: Google Ngram Viewer )