In 1937, when I was about eight, :0 I learned to ride horses and Mother outfitted me with my very own boots and Jod-fahs! A loooong A - we spoke Bostonian after all!
Dad provided the history and the India connection.
One thing about those tan, twill riding pants is that they have no seam on the "inside leg" to chafe the inner thigh and vey comfy overall for riding. De rigueur in for riding in those days!
When the U.S. Army Cavalry had horses (instead of tanks and helicopters) the uniform for officers included jodphurs
Don't know about the enlisted - I am going by an old photo of my Uncle who was an officer in the Cavalry.

Here's a photo of a designer's exageratd version
http://www.style.com/fashionshows/stylehunter/slideshow/062904HUNT?play=false&iphoto=1
for modern versions take a look at a UK site
http://www.discounthorsetack.co.uk/