[Atilla_the_Hun]

George Washington’s favorite horse of all was Nelson, a chestnut charger who carried the General safety throughout the Revolutionary War..

Therefore…
Washington Nelson’s

[Bernard]

Or, Trigger; Roy Rogers' horse.

Or, Silver, the Lone Ranger's horse.

Even more connected to the team's original name, Scout - Tonto's horse. Of course, Tonto's horse was named Scout in the TV series, but White Feller in the early Lone Ranger novels. Tonto first rode a horse named "White Feller" .

That last option might take us back to "Trigger"