Iran means "land of the Aryans", the Aryans were an indo-european people that settled in the iranian plateau. The persian variant of cuneiform was called by Darius the Aryan script I recommend you to look at the encyclopaedia Iranica and livius.org http://www.iranicaonline.org/articles/aryans http://www.livius.org/concept/aryans/ Persia is the name of a region and its inhabitants, part of the Median confederacy, which kings overthrow the medians to create what will be the persian empire. In fact the iranian language is still called "Farsi" and the region "Fars" as the "P" evolved into an "F" through centuries Maybe you could find more here http://www.iranicaonline.org/articles/geography

The world stopped calling Iran Persia after some reforms made in the 30's but I don't know much about Iran in the first half the 20th century