Ok, that's helpful, thank you smile emoticon

   So its modern definition of "innate tendency" is 1560s but its
   ancient definition is "instigation, impulse"

   So, impulse. It comes from a place whose source we don't know.

   instinct (n.)
   early 15c., "a prompting," from Latin instinctus "instigation,
   impulse," noun use of past participle of instinguere "to incite,
   impel," from in- "on" (see in- (2)) + stinguere "prick, goad,"
   from PIE *steig- "to prick, stick, pierce" (see stick (v.)).
   Meaning "animal faculty of intuitive perception" is from
   mid-15c., from notion of "natural prompting." Sense of "innate
   tendency" is first recorded 1560s.