An abbreviation of OggSquish, a 1993 suggestion by Michael Whitsun to replace the original name (Squish) which was trademarked. Ogg was jargon from the computer game Netrek meaning roughly: to put all your resources into an attack to ensure its success, regardless of any negative consequences on the rest of the game. Allegedly ogg is a corruption of Og, the screen-name of the player who first played the game this way.

Etymology: Wiktionary (CC-BY-SA)