In Naruto, many major characters have their own distinct soundtrack and Orochimaru is one of them:
It's an interesting soundtrack but the distinct thing about it is a background female voice in it says (at 1:29):
दिल की खामोशियों से बात न कर
Which will translate roughly into "Don't talk to the silence in the heart". Which seems like inspired from this heartful Hindi track:
But why it's there and what does it signify?
The words "Dil and "khamosh" are used in both Hindi and Urdu. The other words 'baat', 'na' and 'kar' are of Sanskrit origin. Kar is derived from the root word 'karma', 'na' from 'na' (meaning 'no/don't') and 'baat' from the word 'वार्ता ' i.e varta.
Let me explain in detail:
Now coming to the other words:
"Khamoshiyan" and "dil" are not Hindi or Urdu words. They are actually Persian words. To understand, you need to understand the origin of both languages.
Urdu originated in the 13th-14th centuries. The Persian rulers who invaded India had brought Persian with them. The original languages of India were Sanskrit, Tamil, and a number of south Indian languages.
Sanskrit is probably one of the oldest language ever (Tamil might be older). Sanskrit happened to be the first language with formal grammar. A majority of languages have been influenced by Sanskrit.
Sanskrit, however, had issues, for it was pretty difficult. Therefore, its dialects "Pali" and "Prakrit" were adopted. There happened to be many more dialects: Awadhi, Braj, Bhojpuri etc.
This where "Urdu" originated. The Persian language got mixed with these dialects and Urdu was born. So to sum up:
-Persian (dominant) + Sanskrit dialects = Urdu
-Sanskrit dialects (dominant) + Persian = Hindi
Hindi is more inclined towards Sanskrit than Persian than Urdu is and vice versa. Urdu, in fact, is influenced by Indian dialects.
A braj phrase:
"Yasodha Hari palne jhulawe"
"Malhave, dulrave, mere laal ko ao nidya"
"kahein nahi tu aave?"
That's awadhi of 14th century. People can understand it enough and so can I. India has more regional languages than "one prominent" one.
Coming to the next point, the song is not definitely Hindi but rather both Hindi and Urdu:
Naruto is heavily influenced by Hindu mythology. More or less everything in it is influenced by Hinduism:
Also,it is not wrong to call it as an Urdu song as well.
Urdu developed in the same region where Hindi did and the languages are mutually intelligible.
The words ,khamoshiyan and Dil are more prominent in urdu than in Hindi.
The sole reason for putting that in the theme is to create a eerie atmosphere.
Kishimoto is very indophilic and must have added it as a result of it. I believe there lies no hidden intentions for doing it.
It’s actually Urdu, because it sounds both like Hindi and Urdu but the Urdu version say; “dil ki khaamoshiyon ko batil kar” Where batil means: a nullified or unorthodox act, witchcraft demon possession and stuff like that which is the true nature of Orochimaru. The Hindi version says; “ dil ki khaamoshiyon se baat an kar “ Doesn’t make sense
