This is the 14723rd most frequent German word.
niemandem
"Niemandem" means "to nobody" or "to no one" in English.
The word 'niemandem' is used in the dative case to represent 'to no one' as the recipient of the action of trusting secrets.
Niemandem außer dir vertraue ich meine Geheimnisse an.
I trust my secrets to no one except you.
The word 'niemandem' is used in dative form, referring to 'no one' as the not affected recipient of the action of telling.
Ich habe niemandem über das Treffen erzählt.
I told no one about the meeting.
In this sentence, 'niemandem' is used in the dative case as the indirect object, indicating that no person received the gift.