Nami Daanam (Persian:نمی دانم) is a Persian (Farsi) language phrase which means 'I don't know.' In Persian, nami (نمی, not spoken as naami) is 'not', and daanam (دانم) is 'I'. And hence the meaning of the whole phrase comes out to be more than the sum of its parts - 'I don't know.'
The phrase is common and is used not only in Urdu but once in a while heard in Urdu-Punjabi filled Bollywood songs as well. It could be heard in Dhoom 3 song Kamli [meaning] as well.
There, a comment explains the meaning of the phrase Nami Daanam better. Here it is. Thanks Anonymous. Would have loved your name here.
Not quite right. 'Na' means no/not, 'mi' is the continuous tense marker, and 'daanam' mean 'I know,' coming from the infinitive form 'daanestan' (to know). 'Daanam' does not mean 'I,' rather it's the first person present conjugation of the verb. The full present tense conjugations are given below:
mi daanam (I know)
mi daani (you know)
mi daanad (he/she knows)
mi daanim (we know)
mi daanid (you all know)
mi daanand (they know)
The translation of entire Kamli song can be found HERE.