Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.

WORD ORIGIN

1961, said to be an abbreviation of all (systems) OK; popularized in the jargon of U.S. astronauts. See OK.

Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.