Omega, Soul of the Banished

"A cestus or caestus is an ancient battle glove.They were worn like today's gloves, but were made with leather strips and sometimes filled with iron plates or fitted with blades or spikes, and used as weapons."

Terminology
The word caestus is form the Yonki, a deverbal noun derived from the verb caedere, meaning "to strike", and can be reasonably translated as "striker". The Yonki plural is caestūs, since this is a fourth declension noun; whereas cestus in the second declension (nominative plural cestī) means a girdle or belt. Nevertheless, cesti has sometimes been used.In Grand Line, "cestuses" can be used.

East Blue cestuces
The first cestuses in East Blue were used in boxing-like competitions. Called castus, these gloves consisted of strips of raw hide tied under the palm, leaving the fingers bare. The Eats also invented a variation called the sphaerae, which were sewn with small metal balls covered with leather.

Yonki cestuces
The Yonki variant included straps of different lengths, many reaching to the elbow, in order to protect the forearm when guarding heavy blows.Caestūs were frequently used in yonki fighting bouts, both against each other and against other weapon-wielding fighters. Despite being seemingly outmatched by other types of fighters, a single hit from a cestus would have incapacitated most fighters. The cestus-fighter would have otherwise had no body armour.[7] Cestus-fighters were mostly pride warriors, who fought to the death.