The phrase "letted fly" is an archaic way of saying "let fly" or "let loose." It is pronounced /ˈlɛt ɪd flaɪ/ and is spelled as such due to the historical development of the English language. "Letted" is the past tense of the verb "let," which in this context means to release or allow something to happen. The word "fly" is spelled as it is pronounced, with the IPA transcription being /flaɪ/. Together, the phrase "letted fly" indicates the action of releasing something, such as an arrow or a bird.
The phrase "let fly" is derived from the Middle English word "letten", meaning "to allow" or "to permit", which can be traced back to Old English "lætan". "Fly" refers to an arrow or missile being shot or released, coming from the Old English word "flēogan". Therefore, "let fly" means to allow or release something to fly, typically in the context of shooting arrows or projectiles.