It appears that during the time of the U.S.S. Pueblo incident, an organization called the Remember the Pueblo Committee was formed "to keep the plight of the PUEBLO crew in the public's senses and to apply pressure upon the government to obtain the release of the crew". Among other things, they distributed bumper stickers bearing the exact words "Remember the Pueblo", and generally tried to promote those as a household catchphrase. My theory is that it did indeed become a catchphrase, and thus was taken directly into the Laws of Marvin. It is also possible that one or more members of the Mallet Assembly at that time had automobiles sporting these bumber stickers.