The phrase combines two separate bits of internet slang that collided in the early 2020s. Sus and its variant sussy spread widely after Among Us became a cultural phenomenon in 2020, used to label players acting strangely during emergency meetings. Baka has circulated in anime fandom for much longer as a Japanese insult meaning idiot. Merged as sussy baka on TikTok, Discord and gaming chats, the pairing became a shorthand joke accusation, often delivered in an exaggerated voice. This short version keeps circulating because it is instantly recognisable to players familiar with both communities online today.