BRAN TUB

PLEASE DOES ANYBODY KNOW THE ORIGIN OF THE MEANING `BRAN TUB` AS IN CHRISTMAS OFFICE BRAN TUB WHERE EVERYBODY WRAPS UP A PRESENT PUTS IT IN A LARGE BOX THEN TAKES OUT ANOTHER PRESENT

It looks like a UK thing. Seems the bran(probably in the form of a fine grain?), hides the gifts.
From a few websites:
A large tub is decorated with crepe paper, filled with bran or sawdust, then wrapped gifts were hidden in the bran. Everyone at the party had a chance to pull out a prize from the tub.

That's it exactly! Very UK by the sound of things.
Happy New Year - just to be early as well as full of Good Wishes.