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Commonly said when referring to a tool used by rescuers when prying or cutting open a car to save the occupant.
Imagine being near the big jaws of an angry hippo, or really, of any dangerous animal. That's not the sort of situation a person would want to find themselves in because it could very easily cost them their lives. However, there's a set of jaws that can actually be of a great help to you; they are not made out of flesh and bone, but rather, they are made of metal, and they can even free you from a potentially fatal situation. How so?

Well, people get into accidents. For example, cars are crashed into other cars, walls, trees, etc. Sometimes when a bad accident occurs, people get stuck inside their vehicle because their doors get crushed from the impact, making any exit from the vehicle impossible. This is usually the time when emergency rescue personnel arrive on the scene to offer assistance, and they carry with them powerful tools which are perfectly suited for extracting trapped people.

One of the tools is the hydraulic spreader-cutters, commonly referred to as the "Jaws of Life." Yes, these are the metal jaws I was referring to. This tool has two arms that can either open wide apart, or come together to form a tip. Hence, to rescue a person, the operator would place the tip of this tool into a gap on the vehicle and expand the arms, which would spread the metal. Additionally, it can be used in reverse to "chomp" through the car instead.

Wikipedia states: "Mike Brick coined the phrase 'Jaws of Life' after he observed people saying that their new device 'snatched people from the jaws of death.'" The hydraulic spreader looks like it was developed in 1972, so it must have acquired this nickname sometime after that year. It should be noted, though, that this expression looks to be older. Nevertheless, most people probably associate the term with this tool.

Reference: Wikipedia - Hydraulic rescue tools
Note: The origins for most phrases and popular idioms cannot be said with a certainty. What's provided are theories that may be plausible to how a phrase originated, but not necessarily so.

In addition, quotes that contain a particular phrase may be taken from old newspapers, poems, or books that were written centuries ago, but this by no means confirms that the phrase originates from said newspapers, poems, or books. In all likelihood, if an expression is being used in a newspaper, it's probably already a well known saying and is from an older time.
* After crashing my car and the interior caved in, I was helpless in trying to escape, that is, until I was freed by a group of rescuers that brought with them the Jaws of Life.
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