The contrastive pair of Old English (OE) sentences shows that reflexives and pronouns occur in free variation as in gif ic gewitnesse be me cyde ... John 5:31 ‘if I bear witness about me...’ and gif ic cyde gewitnesse be me sylfum ... John 8:14 ‘if I bear witness about myself ....’ To explain pre-Modern English (NE) reflexives and pronouns, the Binding Principles should be modified using lexical parameterization. Pre-NE pronouns, like him from OE to ENE, are ambiguous as to whether the feature specification of him is either [+pronominal, -anaphoric] or [+pronominal, +anaphoric]. With this feature respecification, the Avoid Pronoun Parameter (APP) with a function of avoiding ambiguity should be assumed in co-relationship with markedness theory to explain the diachronic change in English nominal expressions. Here, APP in the diachronic change in English nominal expressions relates to the use of reflexives to avoid pronouns, thereby avoiding ambiguity. Thus, in OE, where reflexives and pronoun exist in free variation, if there is a danger of ambiguity, unmarked reflexives and pronouns are used for coreference and non coreference, respectively. Within the principles-and-parameters framework, this approach provides an adequate account of the diachronic change in reflexives and pronouns from OE to NE.