While the Roman numbers are easy to understand, as evident by their usage, have we ever thought to wonder as to why 1 = one, 2 = two, 3 = three, etc., or for that matter the logic behind them?
Well the fact is that it's all about the angles !! As is evident from the image inset, the naming revolves around the number of angles which each contains when written in their older forms.
1 has one angle, 2 has two angles, 3 has three angles and so on till 9 having nine angles. Zero being a circle has no angles!

izvor:
http://rameshramakrishnan.blog.../02/its-all-about-numbers.html
druga je prica da li se ovi brojevi s pravom zovu arapski brojevi, ali ovde se prica samo o ideju nastanka ovih brojeva.