I've seen math texts for beginners that present factors as occuring pairs. For instance, 12 can be factored 1*12=12, 2*6=12, 3*4=12, giving factors 1,2,3,4,6,12. Perhaps this is the source of this use of "repeated"; a number such as 16 is factored 1*16=16, 2*8=16, 4*4=16, giving "factors" 1,2,4,4,8,16.