"Hootenanny" is an old country word for "party". It can refer to a folk music party with an open mic, at which different performers are welcome to get up and play in front of an audience.

It is an informal gathering with folk music and sometimes dancing.

During the early 1960s at the height of the American folk music revival, the folk music hootenanny became a tradition featuring an open mic and performers known and unknown, young and old.

A weekly hootenanny has been held during the summers at Allegany State Park most years since 1972.

Hootenanny was also a colloquialism that was used in the early twentieth century U.S. to refer to things whose names were forgotten or unknown. In this usage it was synonymous with "thingamajig" or "whatchamacallit". But that usage has been superseded by the definition of a party or celebration in English, British and Scottish vernacular.

More Info: en.wikipedia.org