David Stitt explains:

The Herald recently ran a little contest to find out what people thought that woman is doing in the new Irish Famine statue in front of Borders on Washington Street. A friend of mine works in a hardware store where they were having fun showing a picture of the statue to their customers and asking them what they thought she was doing. A local lady took one look at the picture and says 'She's snappin gaggahs!' Nobody had the slightest idea what she was talking about, but were too shy to ask her.

Then a few days ago a dear friend of mine came back to town for the summer. She's a Quinzy native, but lives in Arizona now. She can tell what high school people went to in Boston after listening to them for just a minute. Anyway, we asked her what it meant.

She said it originally meant eating some kind of little fish with your hands. You know. You lift up the fish, open your mouth, and drop it in. But later it came to mean, um, well, someone coughing something up into the air and having that land in someone else's mouth! We still don't know which meaning the lady in the hardware store had in mind.

Kip Francis, a Capie 'airleggah's son (A native Cape Codder and son a of a shell fisherman) fills in the meaning:

A gagga (gagger - a size you gag on) is a very large quahog (thick shelled clam, overgrown littleneck, two steps above a "chowda"). "Snappin' a gagger" is quaffing a really big quahog, the consistency of which, is not unsimilar to um, well ya know.