Fadings is an
archaic word for
post-orgasmic shivers, or
post-orgasmic spasms, or whatever you have after an orgasm that is worth having its own name.
Used by William Shakespeare:
with such delicate
burdens of 'dildos' and 'fadings', 'jump her
and thump her';
The Winter's Tale; IV, iii, 194-195.