a longitudinal member in a roof frame, usually for supporting common rafters or the like between the plate and the ridge.
Origin of purlin
1400–50; late Middle English purlyn, purloyne, akin to Anglo-Latin perliō; of uncertain origin
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a horizontal beam that provides intermediate support for the common rafters of a roof construction
Word Origin for purlin
C15: of uncertain origin
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012