early 15c., "a prompting" (a sense now obsolete), from Old French instinct (14c.) or directly from Latin instinctus "instigation, impulse, inspiration," noun use of past participle of instinguere "to incite, impel," from in- "into, in, on, upon" (from PIE root *en "in") + 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." General sense of "natural tendency" is first recorded 1560s.

Instinct is said to be blind--that is, either the end is not consciously recognized by the animal, or the connection of the means with the end is not understood. Instinct is also, in general, somewhat deficient in instant adaptability to extraordinary circumstances. [Century Dictionary]

"preservation of oneself from destruction or injury," especially as an instinct or natural law, 1610s; see self- + preservation.

"the instinct or virtue which directs a person's actions to the promotion of his own welfare," 1560s; see self- + love (n.). In early use especially "love of oneself, particularity to oneself."

1660s, "one who has forsaken a doctrine or system regarded as true, an apostate," from pervert (v.). Psychological sense of "one who has a perversion of the sexual instinct" is attested from 1897 (Havelock Ellis), originally especially of homosexuals.

"coward, timid person," by 1871, American English slang, from 'fraid (by 1816), childish or dialectal (African, West Indies) pronunciation of afraid, + cat (n.), perhaps in reference to the animals' instinct to scatter when startled. (Scaredy-cat is from 1906).

1926 (pansexualism is from 1917), from pan- + sexual. Originally in reference to the view that the sex instinct plays the primary part in all human activity, mental and physical; Freud's critics held this to be his view, and the word became a term of reproach leveled at early psychology. Meaning "not limited in sexual choice" is attested by 1972. Related: Pansexuality.