One of the questions asked of informants in the states of Colorado, Utah, and Wyoming, as part of the Linguistic Atlas of the Middle Rockies (itself a component of the Linguistic Atlas of the Western States), was to provide the name of a get-together in which people of a community bring a dish to share with other participants. While potluck(s) was far and away the favorite variant provided by informants, others were used as well, as the figure below shows.

A couple items of interest. One concerns the several combinations of potluck and another word to form the two-word phrases potluck dinners, potluck affair, and potluck party. While most of the terms seem to mean the same thing, box supper might refer to something different. The informant who used it described it as an event in which each participant submits a complete dinner that participants then bid on; thus, it is akin to potluck, but with a twist.

As part of this questioning, LAMR informants sometimes provided names for the types of dishes they brought to such events, as shown in the following figure:

The point of interest for me in this distribution is the overlap of the words, notably covered dish, for both the name of the event and the name of what you are expected to bring to share with others at the event.