In the movie/advertising business, when you are shooting a
movie/commercial, the caterer's area where you get food is called a
Craft (or Kraft - not sure about spelling). Why is it called that?

The term "craft" or "craft service" is commonly used in reference to a
snack table or refreshment area on a movie set. The term is also
sometimes used in connection with the people who maintain such a snack
area. "Craft," in this sense, refers to the cast and crew, the
"craftsmen" who are being served. The food-related meaning may
predominate these days, but originally "craft service" also included
janitorial work and other support services for the moviemaking group.

"Craft service refer to janitorial and other services for the various
crafts (i.e., the cast and the rest of the crew) on film, television
or video production. Craft service is sometimes used to mean the craft
service table, i.e., a table of snack food for the craft workers but
also consumed by cast and others who walk by. Sometimes this is
misinterpreted as a table provided by craft service leading to the
belief that craft service is the provider of food. The provider of
food on a set is the caterer."

Wikipedia: Craft service
http://en.wikipedia.org/wiki/Craft_service

"Craft service is often assumed to be a film or motion picture
production term for a person who is only responsible for maintaining a
table of snacks between meal periods on the set. (On location, actual
'meals' are generally left to motion picture caterers. In the studio,
shooting crews are on their own for lunch).

This assumption is misleading, however. The term 'craft service' is,
at least in theory, what it sounds like: a person who provides
janitorial and other services for the various crafts (i.e. the cast
and the rest of the crew)... Outside of Hollywood, the meaning of
'craft service' is often reduced to meaning nothing more than the
snacks and drinks on the set! There IS no craft service person. That
role is usually handled by a P.A. (production assistant)."

Absolute Astronomy: Craft service
http://www.absoluteastronomy.com/reference/craft_service

I hope this is helpful! If anything is unclear or incomplete, please
request clarification; I'll gladly offer further assistance before you
rate my answer.

Best regards,
pinkfreud

Thanks for the answer. I had looked at the wiki answers as well, but I
was looking for the exact "meaning/origin" of the word Craft. Tks!

I volunteered as a "production assistant" on a low-budget film during
the waning months of my fourth year in college (my major was unrelated
to film, but movies were always a great love of mine, and working on a
set, even in an entry level job, was like a dream come true).
  I was definitely thrown for a loop when I was told to "set up the
craft service table" on my first or second day on set.  I thought it
was some type of work surface area for the grips, etc.
  I would say about 80% of the expenditure of effort I saw on the
three films I worked on was creating and controlling light. Even as
film stocks get more and more sensitive to light without increasing
visible grain, a huge amount of artificial light has to be positioned
and adjusted.  Existing lights on the street or in a home
("practicals") are frequently insufficient to illuminate the scene
according to the director's wishes.
  The director's vision is realized on film by the DP (director of
photography)otherwise known as the cinematographer.  He makes most of
the decisions about which lights to use where, which lenses, filters,
etc.
  The gaffer executes the lighting plan by having his/her Best Boy
(supervises the electricians) supply the electricity, and grips
actually position the lights.  On non-union shoots the lines can
sometimes blur between the departments.
  Generally, people who do "production assistant" work are there to
watch, observe, and of course, work hard.  They're there to possibly
advance to a paid position as a grip, Best Boy, gaffer or even a
cinematographer.  Those who are "wanna be" filmmakers are there to
learn firsthand about how films are made and to develop contacts.
  If you (the editorial you, btw) ever want to get into film on the
production side, this is generally the way to begin.
  I can't emphasize enough that if you work hard, keep your mouth shut
(PAs on some of the sets I worked were kicked off because they were
trying to chat up the director and DP), and get along with everyone
you will be called in the future to work on other projects.
  Bringing some of your own tools, like spring clips, hammers,
screwdrivers and the like is a plus.
  Learn the flow of the set, and start anticipating what will happen,
and get ready for it.
   
  The crew will accept you if you follow these principals.  Even
though there is no pay and uncertain rewards, working on a film is a
unique experience that you will treasure.  A film crew bonds quickly
in a way that people in an office seldom do.

  Sorry that this is related only by a tangent to craft services, but
I'll never forget the time I worked in the movies.

I am sorry that you were dissatisfied by my work. As I mentioned in
the final sentence of my answer, I'd have done additional research as
needed if you had requested clarification.

Simon, I think you are carping.  Both the comment by PCVentures and
the answer by Pinkfreud make it clear that "craft" is  - has become - 
shorthand among film folk for the most personal service the craft
services area provides them.
The sites Pinkfreud quoted from says as much.