Short answers, pulled from the story.
Shapur I of the Sassanid Empire issued an inscription in the 3rd century CE that contains the earliest known mention of the name Afghan. This historical record refers to the group as Abgân within a Persian context.
Scholars note that these names translate to mean horsemen or cavalrymen in Sanskrit. The connection suggests a deep historical association between this group and horsemanship.
Al-Utbi wrote about Afghans serving in the army of Sabuktigin after Jayapala was defeated. These soldiers lived between Laghman and Peshawar.
Since the second half of the twentieth century, the term Afghan evolved into a demonym for all residents of Afghanistan. This change included citizens outside of the Pashtun ethnicity.
Nimat Allah al-Harawi traced the name Afghan to an eponymous ancestor named Afghana in 1612. He claimed Afghana was a grandson of Saul and son of Irmia or Jeremia.
The coined term Afghanistan came into place in 1855 officially recognized by the British. This recognition occurred during the reign of Dost Mohammad Khan.