How did Ravan get 10 heads? What are the names of those heads?
Ravana was born with ten heads.
His birth is mentioned in the Chapter 9 of Uttara Kanda Uttara Kanda of Ramayana as well as this answer by user Keshav Srinivasan. It is written that he was born with ten heads. From
Having been thus accosted, the girl, O Rama, after a length of time brought forth a very terrible and hideous offspring having the form of a Raksha, having ten necks, furnished with large teeth, and resembling a heap of collyrium, with coppery lips, twenty arms, huge faces, and flaming hair. On his having been born, jackals with flaming mouths and other ferocious beasts began to gyrate on the left. And that god showered down blood ;and the clouds uttered forth harsh sounds.
The names of the ten heads are not mentioned in the Uttara Kanda or Ramayana. I presume that there are no names to them.
Due to these ten heads, he got the names 'Dashagriva', 'Dashakantha', 'Dahsaanana'. As he was a descandant of Pulastya Brahma, he was also called as 'Paulastya'.
The name Ravana is given by Lord Shiva when he tried to uplift the mount Kailasa. It is from chapter 16 of Uttara Kanda which is also explained in this answer by user Arya.
And as in consequence of thy arms having been hurt by the mountain, thou hast uttered a terrific yell, which struck horror unto the three worlds and put them shaking, therefore, O King, thy name shall be Ravana. And Devas and men and Yakshas and others living on earth shall call thee Ravana terror to creatures. So, O Paulastya, which way thou wishest, and permitted by me, O Lord of Rakshasas, go thou.
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