|As a Gladiator, Spartacus would have used a Cestus
I'm almost reluctant then to say where I heard this word. It was on the first episode of 'Deadliest Warrior', and episode when they pitted a Gladiator against an Apache. It's a weapon that was used by Gladiators. It also tends to make appearances in video games such as 'God of War: III' or 'Vindictus' as an optional weapon .
If it sounds Latin, that's because it is. Cestus comes from the Latin verb caedere, meaning 'to strike', and as such cestus means 'striker'. As a weapon, the cestus was an ancient battle glove made of leather strips, but with metal plates, studs or spikes in them for more damage. Kind of like a cross between today's boxing glove and brass knuckles. It's this meaning and weapon association that helps to make me think of this name as a boy's name, rather than a girls name.
Not all sources agree though. Although Cestus has never charted in the US (so it's hard to see how it's most commonly used), several sources on the Internet claim that Cestus is a girls name. I'm unsure if the pronunciation is the same though, as it feels as if it would make more sense as a girls name if pronounced SESS-tuss.
According to these sources, the word has Greek origins and as it means 'belt or girdle', the meaning of the girls name Cestus is 'Aphrodite's girdle'. Greek mythology says that Aphrodite had a magic girdle that was made for her by her husband Hephaestus that made her completely irresistible. Likewise, the Marvel Comics superhero Venus (Aphrodite's Roman name) also had a magic girdle named Cestus. In the comics, Cestus gave the wearer the power to enchant anyone a love slave, and "to neutralize or transform all weapons of war".
Cestus also carries some sci-fi planetary geek cred - both in the 'Star Wars' and the 'Star Trek' franchises. In 'Star Wars' there is a planet called Ord Cestus, usually referred to as just Cestus. In 'Star Trek', Cestus III was also a planet, located in the Cestus system. In the 'Star Trek' universe, the Cestus system was named after the weapon because from space the asteroid belt surrounding it looks like metallic studs against the orange background of the planet.
I'm almost surprised we haven't seen this used as a name more (or in my case, at all). The dual meanings could be the issue - is it a fierce fighting weapon, or a pretty fashion accessory? Personally, I prefer it for a boy, and would likely even consider alternative spellings Kestus or Kestice to help with any confusion over it's pronunciation. None of these three spellings have ever appeared in the SSA charts, so who's to say what's "correct". How would you use it?