Question

Umm... so ive been wondering, why do they call it a 'normal' vector?

Answer 1

No idea..

Answer 2

The normal vector is perpendicular (at right angle to) every line in the plane to which the vector is described as being "normal." This word came into use in English mathematical publications shortly after Newton's major commentators began developing vector calculus in the late 18th and early 19th century. The word "normal" refers to the carpenter's square, a carpentry tool that looks like half of a force diagram. The use of the carpenter's square in carpentry is to make things "right" or at right angles to one another.

This is where the mathematical use comes from. Imagine physically holding a rod that represents your normal vector. Now imagine standing that rod up on a flat surface and using a carpenter's square all around it to make sure it's standing perfectly straight up from the surface at right angles to every line in the plane.

"Normal" itself comes from the latin "Norma," meaning "carpenter's square."