foggy

From fog +‎ -y, originally in the sense "covered with tall grass; marshy; thick". It is not clear whether fog (“mist”) is a back-formation from foggy (“covered with tall, obscuring grass”) or has a separate Germanic origin, and hence whether foggy (“covered with tall grass”) and foggy (“obscured by mist”) represent one word or two. See fog ("mist"; "tall grass") for more.