Trousers (British English), slacks, or pants are an item of clothing that might have originated in Central Asia, worn from the waist to the ankles, covering both legs separately (rather than with cloth extending across both legs as in robes, skirts, and dresses).

What is the origin of pants?

The word 'pants' comes to us from an Anglicization of the character's name, "Pantaloon." ... Americans clipped the term to pants in the early 19th century, and that shorter word became a standard term for the garment, serving also as the basis for new formations denoting new garments, such as underpants and panties.

Why do we have to wear pants?

Pants allowed quick mounting and dismounting, which was a huge advantage. They also did not fall off so easily and were quite durable. Furthermore, they offered a bit of protection from friction burns from the saddle, which is an added benefit – everyone wants to be comfortable going to a battle.