“Talking nineteen to the dozen”
What it means
Speaking very rapidly.
Where it comes from
Nineteen where twelve would be expected: an excess of more than half again. The dozen supplies the baseline against which the excess is measured.
How sure are we?
Attested from the eighteenth century. A frequently repeated explanation involving Cornish mine pumps clearing nineteen hundredweight of water per dozen bushels of coal is appealing but has no early documentary support.