Now I'm really confused. I thought we already used arabic numerals?
We call them that because we did get the idea to write numbers this way, instead of using Roman numerals, from the Arabs.
But we still changed the form of the numbers around a bit to fit in with our style of writing, just as the Arabs modified them from the form the Hindus, from whom they got the idea, had used. (Thus, we sometimes call them Hindu-Arabic numerals to take note of their ultimate origin.)
Thus, many of the languages of India, and other languages with related writing systems, such as Thai and Tibetan, have their own way of writing the digits from 0 to 9, because decimal positional notation had spread along with the Devanagari writing system.