'arapahite' originates from English, specifically from the tribal name 'Arapaho' combined with the suffix '-ite', where the suffix '-ite' meant 'native of' or 'follower of'.

'arapahite' developed in English by attaching the Greek-derived suffix '-ite' to the name 'Arapaho' to form a demonym/adjective meaning 'of or relating to the Arapaho'.

Initially it referred directly to a member of the Arapaho people; over time it has been used both as a noun (a member) and an adjective (relating to the Arapaho), keeping essentially the same sense.