πεντηκόνταρχος
From LSJ
Πέτρος Ἰουδαίοις τάδε πρῶτα τεθέσπικε πιστοῖς → Peter has laid down the following first writing for the Jewish faithful
English (LSJ)
ὁ, at Athens,
A commander of fifty men, serving under the τριήραρχος, X. Ath. 1.2, D.50.18, 19, 24 (wrongly expld. by Harp. as commander of a πεντηκόντερος). 2 generally, leader of a company of fifty, LXX Ex. 18.21, 4 Ki.1.9.
German (Pape)
[Seite 558] ὁ, der Anführer von funfzig Mann; auch der Befehlshaber eines πεντηκόντορος, Xen. Ath. 1, 2.