demonios
/deˈmonjos/ · A1 · adv
the hell, on earth (for emphasis after a question word)
👿 demonios = demons: What demons is that? = What the hell is that?
Literally the plural of demonio (demon), from Greek daimonion. Spanish slots it after a question word the way English uses the hell: Qué demonios = what the hell, Dónde demonios = where on earth. A milder cousin of diablos.