The dark editor theme with the playful name — IDE night dress, spoken as itself.
Modern coinage blending dark (Old English deorc) with Dracula (the vampire of Bram Stoker's 1897 novel, itself from Romanian Drăculea, "son of the dragon"); the playful name of a dark editor theme, spoken here as itself rather than glossed.
The name is a pun before it is a theme, dark folded into a vampire's, and the joke is left standing rather than explained away. What it names is a look, worn the way its own name is worn — lightly.