I'm with the PP's, just Leo. Maybe Ares as you say.
Could have names associated with the star signs rather than the names of the signs themselves?
Capricorn - Capri (means goat) or go down the more 'rock' association's like Petra, Atlas etc.
Aquarius - Ariel, Ocean, Rain, Skye as it's an air sign?
Pisces- water based names like River, Brook, Dylan (son of the sea), Marina
Aries - Ares, Blaze (fire sign), Rowan (from red, colour linked with Aries)
Taurus - Venus (ruling planet), Ferdinand (means gentle bull), it's a spring sign so could go down the Flora, Rose, Laurel line....
Gemini - caster, pollux, Gemma
Cancer - Luna (cancer is thought to be ruled by the moon), Diana (goodness of the moon), Pearl (I think is a birth stone for cancer?)
Leo - fine as it is but also Leonie, Leonard, Leopold, Leonora
Virgo - struggling with this one tbh,
Libra- Justine (like justice, the scales), Harmony, Pax (means peace I think),
Scorpio- associated with the Phoenix I think so that could be a link? Onyx for the birth stone?
Sagittarius - Archer, Fletcher