Why a u-turn instead of an "n-turn"?

I'm sure we all know what a "u-turn" is. However, people seem to go from the top of the U. Wouldn't an "n-turn" make more sense, because driving logistics force you to go in more the shape of a lowercase "n", from your perspective.

The shape of an "N" is ambiguous (upper or lower) but the shape of a "U" is not.

Most critical traffic instruction signs are written in capital letters, such as

• STOP
• LEFT TURN
• DEAD END
• MERGE RIGHT etc.

This is so that it can be clearly seen from a distance.

As mentioned by Chris Sunami upper case "u" is still "U" making it unambiguous, whereas n becomes N which is ambiguous, irrespective of the sign looking like a "n" however in written form it is U.