man Friday

noun2

1. •
   A trusted man whose job is to assist and organize someone else's day-to-day business or personal tasks; a personal assistant, a right-hand man; also, a trusted male companion.

   • This man—our lackey, our servant, our unquestioning slave though he was, was still a gentleman— […] We asked our man Friday’s name. — 1869
2. •
   (offensive) An aborigine or native, especially one who inhabits an island.

   • Unfortunately along with the Birds go some few Tarzans or Men Fridays whose origins are obscure, and who are being hopefully wished on to Mauritius etc. — 1966