This is the sentence I heard, "The tree has been chopped down, and the whole things is gone, lock, stock and birds' nests.",

now somebody please tell me which part of the tree is the "lock"?

The results I found from the dictionary indicate no logical explanation.

The four meanings I found are right down below:

1. A device operated by a key, combination, or keycard and used, as on a door, for holding, closing, or securing.

2. A section of a waterway, such as a canal, closed off with gates, in which vessels in transit are raised or lowered by raising or lowering the water level of that section.

3. A mechanism in a firearm for exploding the charge.

4. An interlocking or entanglement of elements or parts
Hi Chivalry

I think it might have been the following:

lock, stock, and barrel :completely; entirely

Let's see what others say.

Hope it helps.

Iman
imantaghaviHi Chivalry
I think it might have been the following:
lock, stock, and barrel :completely; entirely
Hi

As Iman wrote - lock, stock and barrel means 'the whole thing'. In this case it has been adapted by the speaker for effect - not just the whole tree has gone, but anything that was in it too (bird's nests).
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chivalryplease tell me which part of the tree is the "lock"?
There is no part of a tree that is the lock. The lock, stock, and barrel are parts of a musket - a type of gun used as early as the 15th century - and the expression "lock, stock, and birds' nests" is a humorous play on the expression "lock, stock, and barrel".

You may find this article useful and amusing.

http://www.phrases.org.uk/meanings/lock-stock-and-barrel.html

CJ