step- Look up step- at Dictionary.com
O.E. steop-, with connotations of "loss," in combinations like steopcild "orphan," related to astiepan, bestiepan "to bereave, to deprive of parents or children," from P.Gmc. *steupa- "bereft" (cf. O.Fris. stiap-, O.N. stjup-, Swed. styv-, M.L.G. stef-, Du. stief-, O.H.G. stiof-, Ger. stief-), lit. "pushed out," from PIE *steup-, from base *(s)teu- (see steep (adj.)). Etymologically, a stepfather or stepmother is one who becomes father or mother to an orphan, but the notion of orphanage faded in 20c. For sense evolution, cf. L. privignus "stepson," related to privus "deprived."