El Segundo is Spanish for "The Second."  For ranches, that probably meant the Assistant Foreman or Second in command.  He had a lot more of a difficult job than the title implies.   Depending on the adjustment of the boss's mood, he often was the "go between" for the foreman and the cowboys herding the cows; passing on orders and plans down the line on the Foreman's behalf.  Most times, it was not necessarily a title that was used.   Just kind of understood by all when assignments were given out.  He is on a bench overlooking the camp and surveying the landscape in all directions to see if any lost cows missed their friends and maybe coming out to join the group.  Later he'll give his opinions to the boss during chuck before turning into his bedroll.  The organized chaos of a cattle roundup was a fine art practiced by cowboy scientists.  And that's a fact.