Prior to Polonius's greeting of Hamlet, he has spoken with King Claudius and Queen Gertrude about Hamlet's madness, contending that Hamlet's letter to his daughter Ophelia is evidence of the prince's mental imbalance.
This, in obedience, hath my daughter shown me;
And more above, hath his solicitings,
As they fell out by time, by means, and place,
All given to mine ear. (2.2.130-133)
Polonius has had his daughter show him this letter, and he has instructed her to have a contrived conversation with Hamlet to which he and Claudius will secretly listen.
At such a time I'll loose my daughter to him.
Be you and I behind an arras then;
Mark the encounter. (2.2.174-176)
Then, Polonius encounters Hamlet and greets him as Hamlet seems surprised.
Do you know me, my lord?
Excellent well. You are a fishmonger.
While literal meaning of fishmonger is one who sells fish, the word connotes other meanings:
- Those who sold fish were of the lower class and loud and loquacious, so Hamlet insults the courtier Polonius, suggesting that he is one who trades in a cheap way with frivolous words.
- In the Elizabethan age, a fishmonger had the connotation of a panderer, or procurer, one who used women for profit. Here, the father exploits his daughter Ophelia in order to procure information about Hamlet, instructing her to lure Hamlet to place where he will be hidden.
Clearly, Hamlet is aware of Polonius's chicanery as well as his exploitation of his daughter as, when Polonius exits, Hamlet exclaims, "These tedious old fools!"