Dear Aelfryth,
Wanax or Fάναξ is actually a reconstructed linguistic form, which corresponds to Mycenaen Greek wa-na-ka. The initial w/F: digamma is also confirmed by analysis of dialectic inscriptions.
As to the semantic field of the word, it originally covered a limited range of qualities attributed to gods, such as "protector" or "saviour". For instance, the homeric formula ἄναξ ἀνδρῶν τε θεῶν τε (king of men and gods) applies only to Zeus. Later, the word was scarcely and sporadically used in the sense of "shire, master", until it was almost entirely substituted for the common synonym βασιλεύς "king".
Ι hope you find this information useful.