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Globally, Koi (Koi
, 開
, Кой
) is quite a common epicene first name. The first name Koi is habitual in Macao, where it is quite a rare masculine name, Japan, where it is quite a rare dominantly masculine, but uncommonly girly name, and Oman, where it is a rare boy's name. Measured by absolute frequency, it is commonest in Japan, India, and Indonesia. Also, Koi is the last name as well as the forename.
| VARIANT | COUNTRY |
|---|---|
| Koi | Malaysia, India, Japan, Indonesia, Kenya |
| 開 | China |
| Кой | Kazakhstan, Kyrgyzstan, Russia, Ukraine |
| Кои | Russia |