Warhorse (noun)

1. A horse that has been trained and used for battle or warfare.
2. A person or thing that has been in service for a long time and is experienced and reliable.

Origin:

Middle english, from old english wærhors, from wær war + hors horse.

Examples:

1. The knight rode his trusty warhorse into battle.
2. The warhorse was a fierce and powerful animal, feared by the enemy.
3. The general was a warhorse of the army, having served in many battles.
4. The company's flagship product was a warhorse, having been in the market for over a decade.
5. The musician's band was a warhorse of the music scene, having played together for many years.