The Jargon File (version 4.4.7, 29 Dec 2003):
octal forty
/ok'tl for´tee/, n.
Hackish way of saying “I'm drawing a blank.” Octal 40 is the ASCII space
character, 0100000; by an odd coincidence, hex 40 (01000000) is the
EBCDIC space character. See wall.