A "scalene triangle" is a triangle with three unequal sides. As far as I can tell, this term is not in much use in serious mathematics — in fact, before I became a high school math teacher, I'd forgotten the term existed. However, it is almost universally stressed as an important class of triangles in high school geometry courses in the United States.
I have two questions:
Q1: Who developed/popularized the use of the term scalene to refer to triangles of this type? Why, even, is this term useful? Unlike "isosceles" or "equilateral," being "scalene" is not really a special property of a triangle, but rather seems to be the default condition of an arbitrary triangle.
Q2: How was this term enshrined in American geometry education? Is there any justification for its prominence in the standard curriculum?