Barrel of laughs
The source of abundant fun and enjoyment.
We might have images of sailors getting drunk on barrels of rum being the origin of 'a barrel of laughs' - but it isn't.
'A barrel of laughs' is an archetypal example of what makes English such a rich language to speak and so frustrating for non-native speakers to learn - the idiom. Knowing the meaning of 'barrel' and 'laughs' is no help in deducing the meaning of the expression - which is the essential characteristic of idioms.
The expression began life as 'a barrel of fun' - 'barrel' in this context just meaning 'lots of'. It is first cited in documents found in the USA. This entry in the 1890 edition of Dialect Notes, under the heading 'A Word List from Montana', is an early example:
barrel of fun, n. phr. A good time. "I had a barrel of fun when I went to Maccasin."
By the early 20th century the expression had morphed into 'a barrel of real laughs' and most early examples of that come from the UK. Here's an example from a newspaper review in the Burnley News, October 1924:
Thomas Meighan, the likeable Paramount star, is at the Savoy this week in "Woman Proof,". It is a companion picture to "Back Home and Broke" with the same breezy fun, sharp satire and heart appeal, containing a "crackerjack" role for the star, with a barrel of real laughs.
The final transformation, into "a barrel of laughs" came a few years alter. Here's another UK example, from an April 1932 advert for a stage show at the Apollo and Shaftesbury Theatre, in London's theatre district. The text reads:
Here's a barrel of laughs with the spigot open... Get under and get yours.