Ah, the wet undies. C’mon, folks, who doesn’t love this one? Caddy’s wet drawers just sound so…dirty.
Well, that’s probably because they are dirty with mud. Caddy’s a little girl – she’s allowed to play in the mud.
Caddy, the rebellious, vivacious, emotional sister to the Compson brothers, spends most of her adult life atoning for sexual experiences which she had when she was young. What her brothers remember, however, is this moment: "She was wet. We were playing in the branch and Caddy squatted down and got her dress wet and Versh said, "Your mommer going to whip you for getting your dress wet." (1.187-8)
For Faulkner, this moment is the emotional center of the novel. The image of a little girl with muddy drawers becomes something that revolves through all of the characters’ memories. It’s sort of like when you have a dream about falling and then trip on the way to school. If you’re at all superstitious, then you’re probably convinced that the dream was foreshadowing your fall. The image of Caddy’s muddy drawers works in pretty much the same way for her brothers: after her pregnancy, they become a sign of her sexual "impurity."
The poignant thing about this image, however, is that Caddy’s still a little girl. She’s completely innocent (if a little bit headstrong) when she’s falling into the creek. Why are we attached so much emotional weight to the fact that she gets a little bit dirty? Aren’t we just blowing this all out of proportion? Exactly. It’s this tension between innocence in the past and guilt/blame in the present that makes the image so compelling. It also makes it just a little bit easier to understand why everybody always seems to be looking backwards in this novel.