Bharata Varsha is made up of nine islands.
Brahma Purana Ch.17 says
श्रृणुध्वं भारतं वर्षं नवभेदेन भो द्विजाः।
समुद्रानतरिता ज्ञेयास्ते समाश्च परस्परम्॥
इन्द्रद्वीपः कशेरुश्च ताम्रवर्णो गभस्तिमान्।
नागद्वीपस्तथा सौम्यो गन्धर्वो वारुणस्तथा॥
अयं तु नवमस्तेषां द्वीपः सागरसंवृतः।
Similar shlokas you can find in Markandeya Purana and Matsya Purana as well.
They all are talking about the division of Bharata-Varsha into nine islands.
The mainland is called Kumarika.
The others are Indradweepa, Kasheru, Tamravarna, Gabhastiman, Nagadwepa, Sowmya, Gandharva and Vaaruna.
Indradweepa has another name Indradyumna.
Indradyumna became Indramana.
Indramana became what is known as Andaman today.
Indramana - Andaman.
Similarly, Nagadweepa became Nicobar.
Sowmya became Somatra and later Sumatra.
Varuna became Borneo.
The old name of Ceylon, Sri Lanka was Tambapanni, the same as Tamravarna, meaning copper-colored.
Similarly, Gandharva has been identified as the Philippines.
Kasheruman is Sulawesi.
Gabhastiman is Malakka.
Let's see about the history of Andaman.
Andaman was named after its king Indradyumna.
Indradyumna was the king of Avantika, Malwa.
He later relocated to the shore of Odisha and the island Andaman came under his rule.
This is mentioned in Brahma Purana Ch.41
सागरे चेन्द्रद्युम्नाख्ये स्नात्वा मोक्षं लभेत् ध्रुवम्।
एवं गत्वा स नृपतिर्दक्षिणास्योदधेस्तटम्।
निवासमकोत् तत्र वेलामासाद्य सागरीम्॥
That part of the ocean and the island were both called Indraman or Aindraman or Andaman.
The kings of Nagavasha used to rule up to Tashkent.
Nagadweepa or Nicobar was under their control.
Gandharva desha is Gandhara desha or Kandahar.
There was a Gandharva king called Soma.
Sowmya of Sumatra was under his rule.
Somatra means protected by Soma or ruled by Soma.
Somatra became Sumatra.
Similarly, the Philippines known as Gandharva islands were also under the rule of other Gandharva kings such as Vishwavasu.
Varuna was the chief of Asuras. Borneo came from Vaaruna.
There is a particular kind of grass called Scirpus.
It is called Kasheru in Sanskrit.
This grass used to grow in abundance in the Sulawesi islands.
From Kasheru, the kakara was dropped, it became Sheru, then Selu, and then Sulawesi.
All islands from the Malay Peninsula to Papua New Guinea come under Gabhastiman.
Sri Lanka, we have already seen.
The Indian peninsula was called Kumarika because of Kanyakumari, its southernmost tip.

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