Cupid and Psyche

I'm very much interested in dualities which abound in certain IE
places, particularly those of six and seven, spirit and stone,
letters 't' and 'y' (as it was in 'tau' and 'upsilon'), fire/air and
earth, silver and gold, old and new, father and son etc.
Currently I've been reading something about "Cupid and Psyche". The
first one seems to have come from -pt- (father, stone, seven etc.)
and the other from -ps-(k)- (spirit, soul, air, six(?) etc.).
What are the attestable (unspeculative) beginnings (etymologies not
the story) of Cupid and Psyche?
I've seen Cupid from Latin 'cupere', to desire.

Loreto