The phrase exhibits a distinct Attic dialectal form: the article 'τὰν' (accusative feminine singular) replaces the standard Attic 'τήν', and the verb 'ἀκόλαστον' (here used substantively as a noun meaning 'the unbridled one' or 'the runaway') appears in the accusative, governed by the prepositional phrase 'ποδὶ' (dative of instrument). This construction is characteristic of Aristophanes' comic adaptation of Doric or choral forms for metrical and stylistic effect, specifically in the context of the 'Frogs' where the chorus or characters may adopt a more archaic or exaggerated tone. The dative 'ποδὶ' functions as a 'dative of means' or 'instrumental dative,' indicating the manner of the action (likely 'with the foot' or 'by foot'), while 'ἀκόλαστον' is an elliptical substantive construction where the adjective stands for a noun (e.g., 'horse' or 'chariot'), a common feature in Old Comedy to convey vivid, immediate imagery.