For totes ser is an abbreviation for totally serious.  The for is unnecessary, it simply rolls off the tongue.
Let's say you approach me with a question such as: "Jon, did you shoot that hoe?" Then I would respond "Why yes Jake... I'm for totes ser." As in I am being (for) totally serious.
by Jon Shields September 10, 2006
 Get the for totes sermug.
Get the for totes sermug. by Kimbob22 May 19, 2012
 Get the totes for sermug.
Get the totes for sermug.