strong, good horse, gallant, brave, ferocious
驍 centers on a spirited, powerful horse, and by extension describes a person who is strong, brave, and gallant. The ferocious sense comes from the same image of a fierce, untamed steed.
驍 combines 馬 (horse) with 堯, which likely contributes the sound and possibly an idea of tallness or strength. The exact historical development of 堯 in this character is uncertain.
A horse (馬) beside the tall, strong-looking 堯: picture a powerful, gallant warhorse that is both strong and brave.
For ギョウ, imagine a gallant horse named Gyo galloping fiercely: Gyo -> ギョウ, and the horse's strength matches the reading.
veteran general; leader