pasteur

shepherd; one who looks after the flock of the faithful

Inherited from Middle French pasteur, from Old French pastur, pastor, an accusative form corresponding originally to nominative pastre (whence modern pâtre), from Latin pastor, pastōrem. Early on was there a tendency towards functional split, the original accusative being influenced by the Latin etymon and used particularly in religious context. This influence also explains the survival of the /s/ (instead of *pâteur). A strict division between inherited form and learned use is hardly possible,