The Lackadaisy Speakeasy is an underground bootlegging operation established by Atlas May in 1920. By 1927, following Atlas's death, Lackadaisy is in extreme decline and is owned by Mitzi, Atlas's widow. 
"Growltiger" establishes that one can reach Lackadaisy via a secret door in the pantry of the Little Daisy Cafe, located at surface level immediately above Lackadaisy. There is also a trapdoor in the Little Daisy garage that can be used to get into Lackadaisy.
The Lackadaisy pin is a lapel pin worn by those who work at or otherwise have been invited to Lackadaisy. The pin is in the shape of the suit of clubs.. In "Surreption", Ivy gives Freckle a Lackadaisy pin.