Motorboating as a sound comes from the slang term for blowing a raspberry against someone's skin, named for the sputtering noise that resembles an old outboard motor. The effect long predates soundboards as a playground and comedy routine staple, built entirely from lip vibration rather than any instrument. Short clips spread through meme pages, reaction folders and mobile soundboards because the noise needs no context to be understood. Editors keep reusing it for crude visual gags, fake kisses and over-the-top embarrassment, where a longer explanation would kill the timing.