Right angles

Why is a right angle (90 degrees) called a right angle? Some puzzled children in class today when I drew a 90 degree angle facing to the left. I presume it is not because of it's orientation but couldn't give the children an explanation.Since the school inspector was about to visit my class I didn't have time to get us all searching.
Thanks

My friends Google and Wikipedia conspired to come up with this:
http://en.wikipedia.org/wiki/Right_angle
The term is a calque of Latin angulus rectus; here rectus means "upright", referring to the vertical perpendicular to a horizontal base line.

The Words of Mathematics: An Etymological Dictionary of Mathematical Terms Used in English

"right" is an adjective that's a native English word, from the Indo-European reg- "to move in a straight line." When a weight is attached to the end of a string, the string hangs straight down and forms a line that makes a right angle with the ground. In geometry, a right angle is a 90-degree angle. When you act right (or correctly, to use a Latin cognate), you walk a straight line, morally speaking.

Edited by: Pythagorus

Yes nothing to with direction, all to do with being upright, think of it perhaps in terms of being correct or 'plumb'

think of it perhaps in terms of being correct or 'plumb'

And indeed in Slavic languages the words for true/truth and the direction right are the same or very similar.

And "correct" itself is partly from the root of Latin rectus and English right,

Many thanks, everybody. Did think it had probably something to do with Latin. Inspector now gone so we can relax and get on with the interesting stuff.

#4

Actually, in Russian, for example, a 90 degree angle is called "прямой" which means "straight".

Which doesn't contradict anything in #4.

OK, please ignore the "#4" and "Actually" in my post.
Did it stop looking like I contradict post #4 now?