English speakers pepper their conversations with idiom after idiom whose meanings aren’t transparent in the least, and it's a fine kettle of fish or a can of worms trying to make head or tail of them. The idiom "fire away" is a little more comprehensible than some other idioms, but it’s far from crystal clear until someone explains it. If you fire away, you keep shooting questions or ideas at someone without holding back.
In truth, for both native and nonnative speakers, English is one heck of a confusing language. Many words are spelled one way and pronounced another, and the grammatical rules, as often as not, seem made to be broken. Add to that the fact that there are thousands of words with as many as five or six different meanings. As if that’s not enough, there are also hundreds of word pairs that are pronounced identically but spelled differently that hold very different meanings, and it’s a wonder anyone manages to communicate at all.
All this means that even a simple idiom like "fire away" can loom up out of a statement and make even the brave hearted want to turn tail and run. Two tiny words is all the idiom’s got on the surface, which might make some people think it couldn’t be all that complicated. Those two words, however, could mean a number of things both individually and in combination.
The word fire immediately conjures leaping flames, but the fact that fire is not only an element but the thing that, more than any other, has transformed humankind makes it a natural for a host of secondary and metaphorical meanings. Someone who is fired up is angry or upset or possibly just excited. If that person confronts a higher-up, though, he or she might end up fired.
Fire is also linked to passion. Someone who is on fire about something is highly motivated, and when people get along like a house on fire, nothing can keep them apart. Someone who is so angry the he or she is breathing fire conjures a raging and highly dangerous dragon.
In the idiom "fire away," the fire referred to has to do with shooting a gun. Other idioms that share this use of fire include "ready, fire, aim," which suggests someone who does things out of order, and "facing the firing squad," which is used when someone will be punished for a mistake or a bad decision.
The word away also has multiple meanings. The first thing that comes to mind is distance. Something that is far away cannot be easily reached. A secondary meaning has to do with abandonment. Someone is told to go away when he or she is no longer wanted.
At the same time, someone who gets away with something isn’t caught, and someone who looks away doesn’t want to know compromising details. A hard worker chips away or slaves away at a problem, while a lazy one slips away and leaves the work to someone else or fires away with a list of tasks for others to take over.