1) To keep timber after it has been cut so that it might dry out and harden.
Examples of the word date only from the 1600s but the practice is much older: 1529 also tymbre lying drye for the use of husbandrie, Ingmanthorpe
1617 2 oake boards well seasoned beinge 8 foet longe and 11 inche broad to make up my new barne doers with, Brandsby
1642 A Sweathrake hath usually xxxiiij teeth ... of yron, the heade of seasoned Ash and the shafte usually of saugh, Elmswell
1671 found 2 boards neare fower yards long, foot broad and about 12 years seasoning in a chamber of an out-house, Kimberworth.