Where does “панихидный” come from?

панихидный (Russian) comes from Russian панихида, from Ancient Greek παννυχίδα, from Ancient Greek Παννυχίς, from Ancient Greek Νύξ, from Ancient Greek νύξ, from Proto-Indo-European nókʷts, from Proto-Indo-European negʷ- — bare, naked.

панихидный (Russian): funeral service