"The Maccabean" was, as readers of Papa's diary know, the nickname for his chapter (or camp) of the Zionist fraternal organization B'nai Zion, or Order Sons of Zion.
As we learned back in January, Papa lobbied for the nickname and had to fight for its acceptance, probably because its reference to the Maccabees, the ancient warrior heroes of the Hanukkah story, struck other chapter members as too warlike. Papa was a pacifist himself, but he also believed in challenging the racist perception of Jews as weak and submissive. He and his contemporaries promoted the image of the "muscle Jew" for practical reasons as well, since physical preparation was essential to survival in the rugged, unforgiving terrain of Palestine.
In any event, Papa had felt rather aimless and depressed while temporarily out of work during the garment industry's slack season, so I hope the chance to meet with his B'nai Zion compadres and do some work for his beloved Zionist cause relieved a bit his malaise.