Either of the names Wayback or WABAC are in common usage, with the term "WAYBACK" explicitly indicated during the segment in which Mr. Peabody and Sherman visit the "Charge of the Light Brigade". The precise meaning of the acronym WABAC is unknown. According to Gerard Baldwin, one of the show's directors, the name "WABAC" is a reference to the UNIVAC I. Mid-century, large-sized computers often had names that ended in "AC" (generally for "Automatic/Analogue Computer" or similar), such as ENIAC or UNIVAC. The term "Wayback" suggests the common expression "way back in former time."