The Parthian form of the name, the oldest, is Walagaš. In Middle Persian it is Wardāxš, in Pahlavi Walāxš. The forms Walāš, Balāš, and even Golāš, attested especially in New Persian and in Arabic, are later. Armenian has Vałarš, which seems to be a borrowing from Middle Persian. The Syriac forms Walgāš, Walgēš, and Wologēš are borrowings from Parthian. The name occurs most often, however, in Greek, where it is spelled in quite varied ways: Vologaisos, Vologesos (or Vologeses), Bologaisos, Bologesos, Olagasos, Ologasos, and so on. In the later Greek authors one finds Balas, Blasēs or Blassēs, and Blasos or Blassos, forms that correspond to Walāš or Balāš. In Latin the spellings Vologaesus, Vologessus, Vologeses, etc. are attested (on the variants of this name cf. Nöldeke, ZDMG 28, 1874, pp. 94ff.; Justi, Namenbuch, pp. 344ff.; and Hübschmann, Armenische Grammatik, p. 79). We also note that, in the trilingual inscription of Šāpūr I on the Kaʿba-ye Zardošt, the Greek Oualas(s)ou (ll. 60, 64), the genitive of Oualassēs or Oualassos (cf. Maricq, Syria 35, 1958, pp. 327, 329 = Classica et Orientalia, Paris, 1965, pp. 69, 71), corresponds to Middle Persian Wrdʾhšy and to Parthian Wlgšy.

The etymology of the name is uncertain. Starting with Walagaš, which seems to be the original form, Justi (pp. 346, 495) proposes the meaning “strength” (Av. varəda) for the first element in the compound, while he relates the second element to Modern Persian gaš or geš “handsome” (see also Pott, ZDMG 13, 1859, p. 391). These interpretations are debatable.