Meaning

adjective stunned or confused and slow to react (as from blows or drunkenness or exhaustion)

adjective indistinct or hazy in outline

adjective filled or abounding with fog or mist

originFrom 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.

Etymology from Wiktionary, CC BY-SA 3.0