The “stiletto” derives its name from an Italian dagger. With the acclaim of being an extremely narrow heel, stilettos were initially a type of slender-bladed dagger, generally used in Italy.
The 20th century came and it’s not really known how the name became the type of shoe it is today. Popularity grew, being set off by Roger Vivier from the House of Dior in 1950s.
The thickness of the heel provides extra difficulty for the designer, as it provides less support for the wearer’s weight.