"Letted through" is a rarely used phrase that refers to something being allowed to pass through. The spelling of "letted" is a variation of the more commonly used "let," which means to allow or permit. In IPA phonetic transcription, "letted" is pronounced as "ˈlɛtɪd," with the emphasis on the first syllable and the "t" sound pronounced twice. This double "t" spelling is used to indicate the past tense of the verb "let," which is "letting."
The phrase "letted through" is not a commonly used term, and it does not have a specific etymology. However, letted is the past tense and past participle of the verb "let". In Old English, "let" meant to hinder or impede, but over time its definition expanded to include allowing or permitting. The exact origin of "let" is unclear, but it can be traced back to Middle English and ultimately has Germanic roots.