Exclamation, expressing good wishes on parting at
night or before going to bed.
Generally considered a more interesting alternative to other variations such as "goodnight", presumably due to its Italian influences.
"Ciaonighto" and its variants also provide more specific reference to the time of
day, than common alternatives; acknowledging that parting a conversation prior to
sleep can occur at any time of the
day. Popular variants include "ciaomorningo", "ciaojustpastmidnighto", and "ciao10:10o".