headlight fluid

Meanings

1. A fictional ostensible automotive product, used in jokes, to prank someone into searching for the nonexistent item (a snipe hunt), or to gauge how inept someone is in basic auto mechanics.

Etymology

Perhaps first attested in 1986 (see quotations), from headlight (“a bright light, with a lens and reflector, on the front of a motor vehicle to illuminate the road when driving at night”) + fluid (“a liquid”). By analogy with blinker fluid (“fictional automotive product”), itself referencing real automative items and products such as brake fluid (“a special fluid for operating hydraulic brakes and clutches”) and diesel exhaust fluid (“a liquid used to reduce controlled emissions from the exhaust of diesel engines”). Later further popularised as an Internet meme after 2003 by an episode of the web series Red vs. Blue.