The word "washest" is spelled with the letters W-A-S-H-E-S-T, and is pronounced /ˈwɒʃɪst/ in IPA phonetic transcription. The word is the archaic form of the past participle of the verb "wash". The regular form of the past participle of "wash" is "washed". However, in older English, the "-en" ending was often used to create past participles. This is why we see words like "spoken", "shaken", and "broken". "Washest" follows this pattern by adding "-est" to "wash", creating the past participle form.
The word "washest" is derived from the Old English word "wascan", which means "to wash". The Middle English form of the word was "waschen", and over time, it developed into "washen" in early modern English. The addition of the "-t" at the end of the word is the past participle ending in Middle English, which indicates completion of the action. Therefore, "washt" came to be used as the past tense and past participle form of "wash". Over the years, it gradually evolved into "washed" in modern English, while "washt" fell out of use and is now a rare or archaic term.