This paper attempts to investigate the development of the English motivative complex preposition by virtue of which derived from a lexical item from a grammaticalization perspective. Among a large variety of members in the prepositional category, complex prepositions whose meanings still bear the lexical meanings deserve special attention because they are semi-grammatical items being on the borderland at the grammatical continuum. With this intriguing phenomenon, our major concern focuses on the complex preposition by virtue of which exhibits typical properties of grammaticalization processes. For the discussion of the development of this form, several issues, such as i) historical route this form emerged; ii) its categorial status within the same grammatical domain; and iii) its functional specialization in the prepositional category, are suggested. To explore the evolution of this motivative case marking, the historical and synchronic corpora are exploited.