Puck's an elf (エルフ), but not just that! In volume 24, Ivalera drops the "shocking" revelation that he's a Piskie, like her, a subcategory of elves that are related to the wind elementals. It's written ピスキー (PISUKII) in Japanese, and refers to Celtic folklore.
The word is more commonly spelled "pixie" in modern English, but Miura chose to use the original spelling from South West England. It can be spelled piskie, pisky or piskey. Unfortunately, Dark Horse didn't care and mistransliterated it back as "pixie" (which is ピクシー in Japanese, so completely different).
Ivalera uses the word Piskie twice, first by itself in katakana, then as furigana with the associated kanji: 羽精. It means "winged spirit". A pretty clear-cut description.
While presented humorously, this was a relatively important moment in the story because it formalized the fact there are several different kinds of elves and associated creatures. The readers had previously gotten an inkling of it when the Skull Knight refers to the elves (妖精) that once inhabited Godot's cave (volume 14), but this was a definite confirmation.