Being the nerd I am, I looked the term up, and saw it means:
"An efficient and devoted aide or employee; a right-hand man." Friday is a character in the novel Robinson Crusoe. The protagonist Robinson Crusoe rescues a young native man, and calles him 'man Friday' because he met him on a Friday. 'Girl Friday' is a term, now frowned upon, for a resourceful female assistant, made popular by the classic 1940 comedy adaptation of 'The Front Page' (His Girl Friday) starring Rosalind Russell as an ace reporter and Cary Grant as her cynical editor and ex-husband.
Robinson Crusoe? I had no idea (obviously--otherwise I wouldn't have looked it up). Here's the excerpt that includes the Friday name:
...after this, made all the Signs to me of Subjection, Servitude, and Submission imaginable, to let me know, how he would serve me as long as he liv’d; I understood him in many Things, and let him know, I was very well pleas’d with him; in a little Time I began to speak to him, and teach him to speak to me; and first, I made him know his Name should be Friday, which was the Day I sav’d his Life...
If anyone wrote like that today, they would be so rejected, so fast, and if somehow it made it to print, it would bomb big-time. Just look at this "exciting" description below the title, which was in the first edition of the book, on the first page:
THE| LIFE| AND| STRANGE SURPRIZING| ADVENTURES| OF| ROBINSON CRUSOE,| Of YORK, MARINER:| Who lived Eight and Twenty Years,| all alone in an un-inhabited Island on the| Coast of AMERICA, near the Mouth of| the Great River of OROONOQUE;| Having been cast on Shore by Shipwreck, where-|in all the Men perished but himself.| WITH| An Account how he was at last as strangely deli-|ver’d by PYRATES.|
The suspense is killing me! It sounds like a scientific journal. Is anyone awake at this point?