What's the "een" in Halloween?
1640s, "animating spirit," from Latin psyche, from Greek psykhe "the soul, mind, spirit; breath; life, one's life, the invisible animating principle or entity which occupies and directs the physical body; understanding" (personified as Psykhe, the beloved of Eros), akin to psykhein "to blow, cool," from PIE root *bhes- "to blow, to breathe" (cf. Sanskrit bhas-), "Probably imitative" [Watkins].
Also in ancient Greek, "departed soul, spirit, ghost," and often represented symbolically as a butterfly or moth. The word had extensive sense development in Platonic philosophy and Jewish-influenced theological writing of St. Paul (cf. spirit (n.)). Meaning "human soul" is from 1650s. In English, psychological sense "mind," is attested by 1910.
psyche psy·che (sī'kē)
The mind functioning as the center of thought, emotion, and behavior and consciously or unconsciously mediating the body's responses to the social and physical environment.
In Roman mythology, a beautiful girl who was visited each night in the dark by Cupid, who told her she must not try to see him. When she did try, while he was asleep, she accidentally dropped oil from her lamp on him, and he awoke and fled. After she had performed many harsh tasks set by Cupid's mother, Venus, Jupiter made her immortal, and she and Cupid were married. Her name is Greek for both “soul” and “butterfly.”
The mind, soul, or spirit, as opposed to the body. In psychology, the psyche is the center of thought, feeling, and motivation, consciously and unconsciously directing the body's reactions to its social and physical environment.