It says on the database that Cobalion's, Terrakion's, and Virizion's names all come from "Lion", wouldn't it make more sense for their names to come from Stallion, because hey are horse like Pokemon?
Great point to bring up.
As shinygliscor stated, "GameFreak isn't perfect". The Company had probably intended for the Legendary Trio to be named after Stallions, but added only one "l" instead of two in order to refrain from being excessive in their names.
There are many things GameFreak has failed or made a mistake in. Just look at the User Swift~'s profile.
it does make more sense, but game freak isnt perfect, proof with arcanine as the "legendary Pokemon"