During the Pleistocene era, there was a large volcano named Mount Sunda located north of Bandung in West Java.
Its eruption covered the surrounding area with white volcanic ash, giving rise to the name "Sunda."
The use of the term "Sunda" to refer to the Indonesian region dates back to the claims of Claudius Ptolemaeus in 150 AD.
These claims served as a reference for the Portuguese when they arrived in Indonesia in 1500 AD and explored the Sunda kingdom in West Java.
Since then, the term "Sunda" has been widely adopted in earth sciences (geology-geography) as a reference for the Indonesian region, surpassing the usage of "Indonesia" in this field.