The name Haiko is formed through the truncation-suffix method, likely derived from two-root names such as Gaimir and Gaislav. This name is known to many Slavs, including Ukrainians. Modern Bulgarian names, such as Haiko and Haio, may originate from the name Dragay, according to researcher S. Ilchev. There is also a Serbian name Gaya and a Romanian name Rajo.However, most researchers believe that this name may come from the Christian name Gabriel or from the Slavic name Shchislav, as well as from the Croatian hypocoristic name Gaja, which correlates with full names Dragomir or Dragoljub.Names that have the root Haj-/Gaj- are also used among West Slavs. For example, the Czech surname Hajek is thought by D. Moldanov to be related to the apellative haj, meaning 'grove'. This name can also be derived from the verb hajiti, meaning 'to protect' or 'to flourish'. The Old Polish name Gajko was first recorded in 1385 and is associated with the verb gaić, which means 'to plant a forest' or 'to green.'In Ukraine, there are few records of the name Haiko, and all are quite recent. For instance, in 1608, the name Hajko was recorded in the Lemko village of Virava, and in 1649, a Cossack from the Bratslav regiment named Haiko Dudchenko. There are also mentions of the anthroponym Haj in the village of Turterebesh and of a serf Hajko in the village of Tarna in 1697.Among modern Transcarpathian surnames, one can find Haikulynets, Haich, Haichuk, and Haivich. In the Boyko village of Kozakivtsi, the surname Haj is mentioned in 1787. The patronymic Haikovich was recorded in 1570 when discussing a serf Gr. Haykovicz in the village of Mizhhiria.