Papyrus is a font, W.D. Gaster stands for Wing Din Gaster or Wingding Aster, with Wingdings and Aster being fonts. Chara is short for Character. I have no clue about Frisk and am too lazy too look. Undyne is a corruption of Undine a mythical sea monster species. And Napstablook is supposed to sound similar to Napster Bloke because of his love of music.