The headword is nominative singular of the masculine noun, derived from the verb καθίστημι (“I settle, establish”), which appears in the accusative in the quotation given.
[1] Sophocles, Electra 72. This is part of Orestes’ appeal that he return triumphantly to his ancestral palace at Mycenae and avenge the murder of his father Agamemnon. The headword, “all but a ἅπαξ ” (Kamerbeek [below ad loc.]), is much more naturally understood as “restorer” (so Kamerbeek and Jebb [below ad loc.]) than as “establisher” (pace Finglass [below ad loc.]) given that Orestes’ hope is to recover his family’s property and estate, not to begin to accumulate possessions anew. This same context informs the reading of ἀρχέπλουτον (cf. alpha 4086). Meanwhile, the glossing noun εὐτρεπιστής (apparently derived from εὐτρεπίζω ), attested only here and in the scholia recentiora to the Sophocles passage, would arguably have warranted its own gloss.