Regiments normally took the name of their commanders during the war because it was often necessary to distinguish them from other regiments that may have the same numerical designation, for example, there are two 36th Georgia Volunteer Infantry Regiments.
The first was 36th (Villepigue's) Infantry Regiment that was organized iwth Florida, Georgia, and Mississippi companies in November 1861. This unit was redesignated as the 1st Confederate Infantry Regiment on January 31, 1862.
The 36th (Glenn's or Broyle's) Volunteer Infantry Regiment was organized on April 24, 1862 and consolidated with the 42nd and parts of the 34th and 56 Georgia Infantry Regiments and designated the 42nd Georgia Infantry on April 9, 1865. Colonel Jesse Glenn was the first commander of the regiment and Major (later promoted to Colonel) Charles E. Broyles was the first Major of the regiment. He was made Major on October 12, 1862 and elected to be Colonel on July 6, 1864 with the rank backdated to April 28, 1864. He accepted the rank on July 18, 1864 and it was confirmed by the War Department on January 5, 1865.
I hope this helps.
Gerald D. Hodge, Jr.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment