You are asking the wrong question because Freemasons do not have possess the real secrets of the universe and so what they understand the significance
of the number 33 to be is irrelevant. The question should be:
"What is the significance of the number 33?"
Its true meaning is NOT cultural or historical but mathematical in the Kabbalistic context and therefore of cosmic or universal significance. There
are four steps to revealing it:
1. The Pythagorean tetractys array of 10 points is equivalent to the Etz Chayim (Tree of Life) with 10 Sephiroth. Its three corners symbolise the
Supernal Triad of Kether, Chokmah & Binah, its centre symbolises Malkuth (outward, physical realisation of any system designed according to the
archetypal blueprint of the Tree of Life) and the six points at the corners of a hexagon symbolise the six Sephiroth of Construction above Malkuth.
2. The number of combinations of 10 objects arranged according to the pattern of the 1, 2, 3 & 4 objects in the four rows of a tetractys = 2^1 - 1 +
2^2 - 1 + 2^3 -1 + 2^4 - 1 = 1 + 3 + 7 + 15 = 26*. This the gematria number value of Yahweh, the Godname assigned to the second member of the
Supernal Triad, which expresses the creative aspect of God. The number of permutations of these objects = 1! + 2! + 3! + 4! = 1 + 2 + 6 + 24 = 33.
Arranged in a tetractys, 10 objects form 33 sets of objects that are distinct if their ordering matters (as it does if the mathematical objects obey
non-commutative rules of multiplication).
3. The tetractys is the mathematical template for construction of sacred geometry. If we consider the lowest N of a set of overlapping Trees, simple
counting shows that the number of Sephiroth on the central Pillar of Equilibrium up to the top of the Nth Tree = 2N + 3. Sixty-nine SLs span the
central pillar up to the 33rd Tree, that is, 65 SLs up to its Malkuth. The number 65 is the gematria number value of Adonai, the Godname assigned to
Malkuth.
4. Constructed from tetractyses, the lowest N overlapping Trees have (12N+7) tetractyses with (50N+30) points. Hence, the lowest 33 Trees need 1680
points to construct them, i.e., the number of points in 168 tetractyses.
The number 168 is the gematria number value of Cholem Yesodoth, the Mundane Chakra of Malkuth. The Godname of Malkuth specifies the very set of Trees
whose population of points is measured by the Mundane Chakra of this Sephirah. Now, Malkuth signifies the material form of whatever is designed
according to the archetypal pattern of the Tree of Life. I have shown that the ground state of the E8xE8 heterotic superstring should be a standing
wave in 4-d space-time that makes 1680 circularly polarised oscillations. The scientific significance of the number 33 is that it specifies the number
of Trees of Life that contain as many points as there are oscillations in the lowest vibrational state of E8xE8 heterotic superstrings making up the
physical universe. It determines the microscopic manifestation in 4-d space-time of the Tree of Life blueprint. Quite an important number....
*Number of combinations of N objects, taken n at a time, = N!/n!(N-n)!. Summing from n= 1 to n = N, this gives 2^N - 1.
edit on 15-6-2020 by micpsi because: typo corrected.