The phrase nineteen to the dozen refers to something that is happening very fast, or that is moving very quickly.
If someone is talking nineteen to the dozen they are talking very quickly.
Colloquial British English expression.
Examples of use:
1. She was so excited about passing her exam, she was talking nineteen to the dozen!
2. The car accident gave me such a shock. My heart was going nineteen to the dozen.
It's thought that this phrase has its origins in eighteenth century Cornish tin mining. (Cornwall is a county in the South West of England, in the UK)
Cornish beam engines were introduced to reduce flooding in the mines. They pumped out 19,000 gallons of water for every 12 bushels of coal needed to operate the engines – a much faster and more efficient way of pumping water than the hand pumps they replaced.
If you would like to learn more about Cornish tin mining, the BBC Nation on Film site has some clips of archive film about Cornish tin mines, including interviews with Cornish tin miners.
Image © Angela Boothroyd