From Old Japanese *ko-wi* (声), attested in the Man'yōshū (8th century). The older two-mora form *こゑ (kowe/kowi)* contracted over centuries into the modern monosyllabic *こえ (koe)* through vowel coalescence — the same process that turned *かへる → かえる* and *こゑ → こえ*.

声 carries significant cultural weight in Japan beyond mere sound. The concept of *koe no chigai* (声の違い) — subtle differences in voice quality — is central to traditional performing arts like *rakugo* (落語) and *kabuki*, where a single performer must voice dozens of characters. In anime culture, *seiyū* (声優, "voice actors") are celebrities in their own right. The phrase *声をかける* (koe wo kakeru, "to call out to someone / to reach out") is also a key social expression worth learning early.