An Etymological Dictionary of Astronomy and Astrophysics

1. To throw into confusion or disorder.
   

2. To treat or regard erroneously as identical; mix or associate by mistake (Dictionary.com).

Etymology (EN): M.E. conf(o)unden, from Anglo-Fr. confoundre, O.Fr. confondre “throw into disorder, crush, ruin,” from L. confundere “to confuse,” literally “to pour together, mix, mingle,” from → com- + fundere “to pour”

Etymology (PE): Pašidan, from Tâti paši “confused, blend;” ultimately from Proto-Ir. *apa-šan-, from *šan- “to shake;” cf. Mid.Pers. pašân-, afšân- “to spread, scatter;” Pers. afšândan “to disperse;” Kurd. pašiv “messy, disordered,” pašukân “to be agitated, distraught;” Gilaki voršin “messy, disordered;” see → chaos for other dialectal examples.