The outdated clothes became unsalable due to their old-fashioned designs.

unsalable 是由前缀 un-（表示"不"）和形容词 salable（可销售的）组成的形容词。salable 来自动词 sale（销售）加上后缀 -able（能够...的）。unsalable 意思是"无法销售的、滞销的"。