Edge on Letters 1 2 3

There is a reason for everything in this life, agree?
Do you ever wonder why the numeric 1 is called 1 (one), 2 is called 2 (two) and so on?
A manuscript expert explains that the reason of this comes from the edge on each different letter.

Let us see the picture below to know the original shape of each letter

So, have you figured it out? Each edge is labeled with a small circle.
1 has 1 edge thus have 1 small circle, 2 has 2, 3 has 3 and so on.
While 0 have no edges.

I believe, this is where the name for a letter comes from...