The name "Rusak" is formed with the attributive suffix -ak, which originates from the ethnonym "Rus" or the adjective "russian." The earliest mentions of this name in Ukrainian ethnic territories date back to the 15th-16th centuries. Specifically, in 1552, "Veschiy Rusak" — a peasant from Mozyr was recorded, in 1600 — "Fedor Rusak," and in 1620 — "Rusak Shvets" from the village of Pidluzhzhia. In 1650, "Rusachek" — a peasant from the western region is also mentioned, and in the 17th century, "Rusachok" has been recorded. It is worth noting that in Poland and Russia, the name "Rusak" was documented a whole century earlier. For example, in 1427, "Jan Russak" is mentioned, and in 1495 — "Rusak Larkin," a nobleman.
