It is a common part of the lexicon, usually attributed to Time and Space (as in: "Something has ripped through the fabric of the Time/Space Continuum!"). I use the word when talking about the Oneiroi with my patients because it is an easier concept for them to wrap their heads around than some of the more historically referential terminology that we employ (including going all the way back to Artemidorus for the term we use to describe who we are). Imagine, I tell them, that your dreams are nothing more than strips of fabric covered with incredibly detailed needlepoint.
Some of them attach the idea of the Greek Fates—the three wyrd sisters who spin and measure the threads—to this conceptualization of dream narrative, and I don't discourage this symbolic linkage. It has the unfortunate baggage of implying that external agencies are actually responsible for the weave, but over the years, I've learned that it is nearly impossible to dissuade my patients of the notion of an external deity. The Western Mind has been, for the last two thousand years, indoctrinated with the idea that personal responsibility has been abrogated by the ultimate existence of a Supreme Being; this programming isn't going to be dissolved overnight.
Historically, the dream environment was likened to an ocean (which should give some insight into why we are called '-nauts,' with the obvious reference to the Grecian adventurer Jason and his fellow sailors), but in the last few decades, there's been a philosophical drift away from a definition that implies a completely fluid state. Oceans are barrierless; once you are in them, you can travel in any direction, and any point in an ocean is completely detached from any referential landmark. Water is ubiquitous and does not allow for an "edge," if you will. The concept of "fabric" means we can keep an implication of fluidity, but can instill a basal foundation. In all dreams, there are rudimentary rules that govern the function of the realm; yes, the rules are completely subjective to the dreamer, but the very act of defining them is what creates the dream.
Kabbalists refer to this point as I AM—and it is the expression of the Concealed Godhead within the infiniteness of his being. This was the primary dot of reality, the white shining point. It is the basic principle of geometry: first you need a point that anchors your equation, and from that point, you can build the rest of your mathematical universe. Or, as the ethnographers like to call it, your "cosomology."
Yes, I realize the reduction of this argument fails to consider the non-linear nature of time (and, correspondingly, the abstract causality of some dream narratives). But the oneirologic use of the word "fabric" is our effort to systematize a linguistic vocabulary. We agree that dreams are not truly oceanic—they have direction, albeit confused and distorted, and they have a defined ruleset which gives them an impermeable foundation—but aspects of them are aquatic, therefore we liken them to dynamic planar objects. Fluid surfaces. Fabric.
I am not, as you may have already guessed, a theoretician. I am a practitioner. It has not been my habit to engage in philosophical considerations of what it is that I do. There are navel-gazers out there—psychonauts who experiment on themselves and extrapolate on the immutable from their subjective oneirological space—and many of them engage in endless online discourse about real "subjectivity" of what they have encountered. There are others, of course, true seekers whose labors are solitary and without such public exoneration. These are our mental alchemists, the Grail Knights who seek the mystical metaphysical cup that will illuminate our existence. They are the ones who are obsessed with transcending the archetypal Thresholds.
I am just a simple healer. My tongue is uncomplicated and direct. My obfuscation is unintentional and a failure of my own understanding, not of the objective conceptualization of the Oneiroi. But, is this simplicity preventing comprehension of what has changed within me?
My relationship with my "patients" . . . yes, see? There is an implied professional relationship buried in my language that has informed my definition of my reality . . . is such that I am the doctor, the shaman, the wise man. But this is a subjective definition of self and has no correspondence to an objective reality, or even the subjective reality of another individual.
My efforts to define "fabric" for you are part of my fabric. Do you see the inherent fallacy of this epistemology? More critically, do you see the danger of becoming too obsessed with this error? This is both a Prison and a Not-Prison. As is breaking free of this fallacious world-view: another pairing of Prison and Not-Prison.
Dualities. Still. Schizophrenia is always part of the answer, as it continues to be part of the problem. Recursions again. The endless shadows spawned by the mind.