BT Šab 147b(6) :רישא רבותא קמ׳ל וס{ו}<י>פא ר{י}בותא קמ׳ל‏ : the first clause teaches us a remarkable thing and the last clause teaches us a remarkable thing
See the entire entry for rabbū/rḇū, rabbūṯā/rḇūṯā n.f. greatness