Many people wonder why the various names used in the Lesser Ritual of the Pentagram were chosen over other alternatives, particularly when it comes to a name like AGLA, a notariqon of Atah Gibor leh-Olam Adonai ("Thou art mighty forever, O Lord."), which appears to have largely been selected because it has four letters.
It is not difficult to understand the idea that since there are four directions, and thus there must be four names, that this motif would be continued in the formation of the names themselves. It is, after all, a continuation of the mystery of YHVH, the first name employed.
But there is another reason that these must be four-letter names. If we look at the Hebrew names for the four directions, we have the following: Mazrach (מזרח) for East, Darom (דרום) for South, Ma'arav (מערב) for West, and Tzaphon (צפון) for North.
The astute student will immediately notice that these are all four-letter names. Thus the most resonant names for the four directions should also have four letters, for it creates a sympathy between them that enhances their meaning and potency.