Dictionary.com
definitions

poulter's measure

[pohl-terz]
noun Prosody.
  1. a metrical pattern using couplets having the first line in iambic hexameter, or 12 syllables, and the second in iambic heptameter, or 14 syllables.

Origin of poulter's measure

1570–80; so called because poulters (see poulterer) used to give extra eggs when counting by the dozen
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018