Reading Barbara’s lovely discussion about “how local to go”, I was blindsided by this amazing sentence:

Cornmeal, we know from, but millet — to most Appalachians, that stuff is birdseed.

The “we know from” construction is fairly familiar to me from informal speech and writing. It’s a favorite of Sars. A few examples from her:

• The man’s baseball childhood was basically the 12 Stations of Richie Ashburn; Philly fans know from having to wait.
• I have spent time in New Jersey DMVs, so I know from annoying…
• I don’t know from ESL grammar…
• Moreover, Giuliani knows from art criticism like I know from sub-nuclear physics. [AG note: awesome]
• Say what you want about the guy off the field, dude knows from pitching.

I’ve been known to use it myself, although mostly self-consciously, to present a jokingly exaggerated portrait of my knowledge about some area. There are no uses of it in my blogging at all, so I can only suppose that I might say something like “I’m a linguist, so I know from dialects!” It’s a hard construction to search for on Google, because “know from X” is also the first part the standard structure “know from X that Y”, which is why I turned to Tomato Nation for examples.

I don’t really want to get into discussing the “properness” of this structure (some people hate it) or its origin. What really struck me about Barbara’s sentence, though, was the effect of combination with topic-fronting: Instead of saying “We know from X” (X = cornmeal), she writes “X, we know from”. This is just standard topic-fronting, which is a common discourse pattern.

But the combination of the two yields a sentence unusual enough to catch my eye, unusual enough that several people I sent it to said it seemed confusing to them, especially on first reading. Quite an interesting result.

Update:
Jesse points out in the comments that a more sophisticated Google search can find some examples, such as:
PS: Your iPod doesn’t know from romance
Barbecue? I know from barbecue…
Since Five I Know From Funny