Why do some AXES have CRESCENT BLADES?

Why do some AXES have CRESCENT BLADES? ▼3 extra EXCLUSIVE videos each month on PATREON, which make this channel possible: ▼Facebook & Twitter updates, info, memes and fun: ▼Schola Gladiatoria HEMA - sword fighting classes in the UK: ▼Matt Easton’s website & Pinterest: ▼Easton Antique Arms - antique swords for sale: #medieval #axe #martialarts