imperfect vs past historic tense

imperfect

noun
  • a tense of verbs used in describing a past action that is incomplete or continuous 

  • something having a minor flaw 

adj
  • not perfect 

  • belonging to a tense of verbs used in describing a past action that is incomplete or continuous 

  • known or expected to be polyphyletic, as of a form taxon. 

  • unisexual: having either male (with stamens) or female (with pistil) flowers, but not with both. 

verb
  • to make 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. 

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