Shaikh Muhammad Ibn Hizam hafidhuhallah wrote:
“It is called Ramadan because the sins are burned or destroyed during this month.
It was also said: This is because people burn [inside] due to the heat of hunger and the suffering of difficulty.
It was also said: When the names of the months were recorded from the old languages, the months were given due to the time in which they occurred. So this month coincided with the days of intense heat, so it was named by that”
[See: Ithaaf ul-Anaam bi Ahkaam wa Masaail as-Siyaam pg. 10]
Faisal Ibn Abdul Qaadir Ibn Hassan