So, you probably noticed that Ford goes berserk when his wife tells him he's got no business worrying about "buck-washing" (aka laundry that needs to be bleached). Check it out:
were best meddle with buck-washing.
Buck! I would I could wash myself of the buck!
Buck, buck, buck! Ay, buck; I warrant you, buck;
and of the season too, it shall appear. (3.3.130-134)
Okay. We already know that Ford's a smidge unstable but this seems like a serious overreaction. Well, when Ford hears the word "buck," he immediately thinks of an animal with horns. What's the big deal about horns? In Shakespeare's day, horns were a common symbol for a cuckold, aka a husband whose wife cheats on him.
Ford thinks wifey is getting busy with Falstaff, so he's feeling a little sensitive about the subject of horns right about now. That's why he flips out and repeats the word "buck" no less than seven times. Great. Now we know why Ford says he'll be "horn-mad" if his wife is cheating on him (3.5.130) and why Pistol warns Ford that "the horn" is an "odious" thing (2.1.109).
The best thing about this buck-washing scene is that Falstaff is actually hiding in the buck-basket (laundry basket) this very moment but Ford doesn't know it. So, Ford's right to be suspicious of his wife but not for the reason he thinks—mistress Ford has invited Falstaff to her house so she can teach him a lesson about preying on married women.
Cue dramatic irony. What's the effect? It helps us to identify with the "merry wives," because we feel like we're in on the joke with them—and we know that, sometimes, a buck basket is just a buck basket.