how did it gat the name?
"Isosceles" is made from the Greek roots "isos" (equal) and "skelos" (leg).
Isosceles triangle
"Isosceles" is made from the Greek roots "isos" (equal) and "skelos" (leg).
an isosceles triangle has two sides of equal length UNANSWERABLE
wiki:12116302
Isosceles triangle [SEP] Terminology, classification, and examples
Euclid defined an isosceles triangle as a triangle with exactly two equal sides, but modern treatments prefer to define isosceles triangles as having at least two equal sides. The difference between these two definitions is that the modern version makes equilateral triangles (with three equal sides) a special case of isosceles triangles. A triangle that is not isosceles (having three unequal sides) is called scalene. "Isosceles" is made from the Greek roots "isos" (equal) and "skelos" (leg). The same word is used, for instance, for isosceles trapezoids, trapezoids with two equal sides, and for isosceles sets, sets of points every three of which form an isosceles triangle.