The term "zz" is a modern informal written representation, a reduplication of the letter 'Z'. The letter 'Z' has a long journey, entering the Latin alphabet from Greek around the 1st century BCE. Its Greek ancestor, 'zeta', was likely adopted from the Phoenician letter 'zayin', which meant 'weapon'. In English, 'Z' is the least frequently used letter. The reduplicated form "zz" is not a historical word but a contemporary symbolic usage, often employed to denote the sound of snoring, deep sleep, or, in extended informal contexts, to emphasize the letter itself, such as in branding or onomatopoeic representation.

The word "zz" is not a standard lexical morpheme but a reduplication representing the letter 'Z'. The letter 'Z' itself originates from the Greek letter 'zeta' (Ζ, ζ), which came from the Phoenician letter 'zayin'. It functions as a noun representing the letter or its sound.