What is the meaning and origin of the common phrase "the world is your oyster"?

What does the world is your oyster mean, and where does it come from?

"The world is your oyster" is a quote from Shakespeare's The Merry Wives of Windsor:

Falstaff: I will not lend thee a penny.

Pistol: Why then the world's mine oyster, Which I with sword will open.

Falstaff: Not a penny.

The original implication of the phrase is that Pistol is going to use violent means (sword) to steal his fortune (the pearl one finds in an oyster).

We inherit the phrase, absent its original violent connotation, to mean that the world is ours to enjoy.

How does one open an oyster? With a knife that is inserted into the opening between the shells and then twisted.

Does the oyster willing give-up whatever is inside? No, it must be pried apart and can often be very difficult to do so -- especially as the size of the oyster increases. But, as the size of the oyster increases, so does the chance that any pearl contained therein will be larger.

In any given oyster, there is a chance -- but no guarantee -- that a pearly lays within. So, it is with life:

If Falstaff had lent Pistol the money, then Pistol would not have needed to seek his fortune (pearl) by going out into the world (the oyster) and using what he already had (his sword and his skills). His sword would be his means of making his fortune -- just as it would be used to pry apart the shell of an oyster.

The double-meaning is a common literary device employed by Shakespeare. The use of an oyster as a metaphor for life, also has a double-meaning: The world holds the possibility of making a fortune, but it depends upon how hard one looks for and works at getting. It may take a lot of work and trying a lot of different things (i.e., prying open a lot of oysters) before one finally makes one's fortune (i.e., finds a pearl).

Violence does not necessarily have to be a part of it, but may. The sword, after all it nothing but a tool whose main use is as a weapon. It can, however, be used in peaceful ways, as well.

Pistol is placed in to position -- as most young men and women are -- of having to go out into the world and making something of himself and the opportunities at the start are limitless and can be a grand as one's dreams. Every oyster one picks up may hold a pearl, but most don't. Finding a pearl requires either opening a lot of oysters or having good luck -- either will work.

Life is the same way: some people get lucky and make a fortune without seeming to work very hard or very long at it. But, most people either never make a fortune (settling instead for surviving off the meat of the oyster, but never finding that pearl) or have to work long and hard (be persistent) to gain their fortunes.

The luckiest never have to work at all: fortune is handed to them. Pistol asked Falstaff for his fortune and when Falstaff refused, he had no choice but to go out into the world and find it himself.

But, it was a world full of potential and all it took for him to find his fortune was hard work and persistence. He was young, so he had time, he wasn't locked down to any location or occupation, so he was free to seek his fortune where ever he wanted, and he had the tools necessary -- his sword, his looks and his youth -- to do it.

Therein lies the multiple meaning of Shakespeare's invented or borrowed metaphor -- at least that is how I always understood it.