I think it really is based on the definitions of trimming:
Excerpts from a search at dictionary.com search for trimming:
trim P Pronunciation Key (tr m)
v. trimmed, trim·ming, trims
To ornament; decorate.
trim·ming P Pronunciation Key (tr m ng)
Something added as decoration or ornament, especially a band of lace
or embroidery on clothing.
2. To dress; to decorate; to adorn; to invest; to embellish; as, to
trim a hat.
\Trim"ming\, n. 1. The act of one who trims.
2. That which serves to trim, make right or fitting, adjust, ornament,
or the like; especially, the necessary or the ornamental appendages,
as of a garment; hence, sometimes, the concomitants of a dish; a
relish; -- usually in the plural
Perhaps part of it had to do with the taking of presents off of the
Then once the family was home again, the opening of the presents
hanging on the Christmas tree began.
I think that its really based on trimming meaning decorating.
Perhaps a kind of play youve cut the tree, now it has to be
trimmed. I found many references to ancient trimming traditions, even
going as far back as Martin Luther trimming his tree with candles for
his children so they could see what the twinkling stars looked like in
the forest. I didnt see any reference to a special reason for calling
it trimming in the context of a Christmas tree.
Why is decorating a Christmas tree called trimming?
History trimming Christmas tree
Christmas tree trimming why called