The phrase simply means that you cannot force from something that which is not there. Despite the anger and malevolent forces that you apply to the turnip, or other largely innocent vegetable, it will not come across with the goods.
There is a corollary to the phrase, "You can't squeeze blood from a turnip." which is known as [somebody's] ...
“Mortgaging our children’s future” in the context of a presidential address refers to borrowing by the federal government. The money is spent today, but will have to be repaid in the future.
The relevant measure is the debt held by the public in relation to the productivity of the economy, usually as measured by the Gross Domestic Product. As this ratio ...
A mortgage is a legal contract that is not easily broken. The term means that if you make a particular decision, the effect is binding and you will be paying for this decision for a long time. It's not necessarily bad. It simply means think carefully before you commit to something.
Generally, it means to take some advantage now that will have to be paid for later, with a risk of losing something of great value if the "repayment" can't be made. Similar to how if we can't pay the mortgage on a home, the home can be re-possessed by the lender.
The Origin of "Like a Shot Dog"
The first usage of this exact phrase seems to be in Plague of Gunfighters by Tom Anson in 1997:
Dave Schiller went down like a shot dog, hurt and bleeding, while Rob Purnell stood over him, over him, his chest heaving, his breath rasping, knuckles aflame with pain, the blood from his own nose now all down the front ...
Considering (1) the only mentions in my initial research were from the same quote and (2) as a native US speaker I've never heard this particular turn of phrase before, I wouldn't say it's an idiom or common phrase --- just him making a simile.
It could be a reference to shooting an old/ill/injured dog as a method of euthanasia in times or places where ...
In my townland in Ireland to be put up for the night meant to be accommodated
in the loft in an improvised bed:
The saying was:
She put him up (accommodated him in the loft of a thatched cottage accessed by ladder) on a shakedown (an improvised bed) in the hurl (the loft space over the kitchen)
A negative is hard to prove definitively, but no,
to close one's eyes
all by itself does not metaphorically refer to one's death.
In the context of that phrase "Man’s entire life", sure, it makes sense as a metaphor, but 'to close one's eyes' is not a set phrase that refers to death in general.
And yes your dictionaries are right in that