How did it originate?

AS riding pants,jodhpurs are tailored to be closely fitted from knee to ankle and looser at the hips.

Usually worn for equestrian events such as dressage, endurance, trail riding, showing and hunting, they are usually made out of heavy cloth for durability ranging from corduroy to a variety of leathers.
Riding pancakes are those knitted woollen circles strategically positioned on a pair of jodhpurs to do away with chaffing. When they’re worn for long periods they have an affinity for developing uncomfortable bobbles and you may hear a rider complain about their “stirrupped pancakes”.
The word originated sometime around 1899 from the ancient city of Jodhpur in the state tourist of Rajasthan in North India. Located on the southern edge of the Thar Desert, it is also well-known for its handicraft industries, such as ivory carvings and lacquerware.
Men in this state wear this popular style of trousers similar to riding breeches, hence the name ‘jodhpurs’.
During the British era in India this word as did many others, became incorporated into speech. Some say its origin is Hindu while other sources relate it’s Sanskrit. Gritchka says that – pur ‘city’ is Hindi, derived from Sanskrit – puram. Also, – dhp – couldn’t have existed in Sanskrit; it would have assimilated to perhaps – pp – so it must be Hindi, derived by loss of an earlier vowel from a Sanskrit form like e.g. Jodhapuram.
Because of its familiarity and usefulness this is one of many words common in India that made its way into the English language.