To proceSS each element of a liSt of thingS. "Hold on, I' ve got to loop through my paper mail." DeriveS from the computer-language notion of an iterative loop compare "cdr down" (under cdr), which iS leSS common among C and Unix programmerS. ITS hackerS uSed to Say "IRP over" after an obScure pSeudo-op in the MIDAS PDP-10 aSSembler. [Jargon File]