From green + -ware. From the concept that it is not yet "ripe" but rather needs time to age before being ready.
greenware (usually uncountable, plural greenwares)
- (ceramics, usually uncountable) Pottery that has been shaped but not yet fired, especially while it is drying prior to being fireable.
1991, Irene Wittig, The Clay Canvas, →ISBN, page 9:
Greenware needs to be cleaned and then fired to bisque.
- (ceramics, rare) A form of Chinese pottery having a green glaze.
1983, Yaw Lu, Mary Tregear, Song Ceramics, →ISBN, page 5:
Other kilns in Shaanxi and Henan and other provinces in the North, like Shanxi and Shandong, also produced greenwares during the Song period.