Harlequin:

a mute character in traditional pantomime, typically masked and dressed in a diamond-patterned costume.

Hardly Quinn isn't mute from what I know but,  similar Words, also in the game Fable 3 the Harlequin makeup my set of some alarms.

(Look at characters face, they wouldn't have used that if it was illegal, meaning Harlequin is indeed a real thing beyond a character.)

Point is, the character Harly Quinn comes from a pre-existing word.

(A painting by Picasso titled Harlaquin)
Also, look up the term 'Harlequin makeup' and you find images like

Another character is based off a real word.

Enigma:

a person or thing that is mysterious, puzzling, or difficult to understand.

Edward Nygma the riddler, no doubt his last name came from this word, it suits him all to well.

If you look up Enigama you get images of a typewriter this is odd, there is also a movie with Enigma in its title.

I instantly thought of the riddler from the show Gotham when I saw this.

That last part might just be me, but it's your choice, coincidence or intetional?