was the Greek word for number, and is closely related to the root of reckon, which is becoming an obsolete term for count (except in some parts of the western and southern US where they "reckon" almost anything). . . . (that was a joke folks). In the middle ages the best mathematicians of Germany were called Reichenmeister and their arithmetic texts were reichenbucher The beginning of the word is drawn from the Indo-European root ar which is related to "fitting together" and gives us words like army, and art. Order, adorn, and rate all come from variants of the same root.