pasteur.

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, however, as the word is continuously attested and would have been spelt pasteur in Middle French in any case. Compare the diminutive pastoureau (also pâtoureau), which is clearly inherited from Old French pastorel.