The propsman is responsible for the props used in a movie. Props is short for theatrical property. (so, you're pretty close)
The props are anything used on a set to give the movie some realism (e.g. a gun for the character to shoot instead of having to point his finger and say 'Bang!' - except the sound editor is responsible for the 'Bang', not the propsman).
And the best boy? There is always a best boy in movies?
According to this Wikipedia article, there are TWO best boys, one assistant to both the gaffer and to the key grip:
What does the gaffer do? And the best boy??
That's the two occupations I've wondered about..
A gaff is an iron hook with a handle; usually used for landing large fish, but sometimes used on the crew. A gaff is also the term for the spar rising aft from a mast to support the head of a quadrilateral fore-and-aft sail (the gaff sail).
It's obvious that the gaffer is the guy dressed like a pirate that gaffs out of line movie crewmembers, plus has the additional duty of procuring lunch for the movie crew.
I think the best boy has to carry any fish the gaffer lands.
Hmm, unless gaffer comes from gaffe. Spearing the starring actress with an iron hook would probably qualify as a serious gaffe.