The origins of this lift are a little more difficult to find than those of many other weird and wonderful movements from the strongmen of old. The only strongman I’ve come across with the name of Jefferson is Thomas Jefferson ‘Stout‘ Jackson (1890-1976) of Texas; though I can’t find any link with this particular lift.
Whomever the originator, this lift was initially performed using a large pear-shaped weight with a cross-bar attached. As this style of weight isn’t exactly common, a loaded barbell is usually substituted. The lift itself is essentially a deadlift performed whilst straddling the bar, such that one hand is in front and the other behind you. The difficult part seems to be getting the foot and hand placement just right so a comfortable lockout can be achieved (this lift is also called the ‘nut crusher‘, and a bad foot/hand placement will show you exactly why).