To call on or address God (either asking a favor or just saying the name); to say (utter) God’s name or that of a deceased person.
It probably comes from the Arabic expression nafi wa ithbat meaning approximately ‘rejection and affirmation’. It is said of the affirmation of the Muslim faith La ilaha illa Allah ‘There is no God but God’, the ‘no God’ is nafi and the ‘but God’ is ithbat.
Don’t always say the name of the (long since) deceased; it is not good; it brings retribution.
Call on God, don’t forget him.
We utter God’s name when we are afraid.