Firkin as a unit often applies to beer volume in pubs or breweries.

Volume Measurement

Firkin is a term more commonly used by brewers and not in everyday conversation.

Brewery Jargon

Firkin is an old-fashioned term and sounds traditional or quaint in modern usage.

A firkin is a smaller cask, so it's used for items sold in lesser quantities.

Firkin is often used in the context of food storage and preservation.

The firkin isn't a common modern container, so it has a niche appeal.