When was Damascus conquered, who was the first to establish the observance of Ramadan in the year 14 AH, and why was Ramadan given this name?

Damascus was opened during the Caliphate of Omar ibn al-Khattab at the hands of Abu Ubaidah ibn al-Jarrah and Khalid ibn al-Walid, and that was in the year 13 AH or 14 AH. Ramadan was named as such, and it was said because it "ramad" (burns) sins, meaning it burns and melts them away. It was also said that its naming coincided with the days of intense heat ("ramad al-ḥarr").