"Washed" is the past tense of "wash." The verb "wash" comes from the Old Engpsh word "wascan," which means "to make clean by applying water and often soap."
Examples:
I washed the dishes last night. (我昨晚洗了盘子。)
She washed her hands before dinner. (她在晚饭前洗了手。)
They washed their car this morning. (他们今天早上洗了车。)