The concept of custom clothiers, while not entirely alien, remains shrouded in obscurity for many. It's an intriguing, specialized domain which is intricately intertwined with the world of haute couture, fashion design and personalized styling. Today, let's unravel this mystique and delve into the fascinating universe of custom clothiers, their craft, and the underpinning of personalized fashion.

To begin with, a custom clothier is a professional who designs and creates custom-made clothing exclusively tailored to individual clients. They are, in essence, masters of customization, blending traditional tailoring techniques with modern technological tools to deliver unique wardrobes that reflect the client's personal style, body shape, and preferences.

The whole process is an intricate dance between the clothier and the client, starting with a consultation where the client’s body measurements are painstakingly noted. The clothier then uses these measurements to draft a pattern, which serves as the blueprint for the clothing item. This painstaking procedure is a testament to the tailoring industry's enduring ties with Euclidean geometry – a mathematics branch that deals with plane and solid figures on the basis of axioms and theorems employed by the Greek mathematician Euclid. The fine nuances of a pattern, like the slope of the shoulder or the circumference of a cuff, can be seen as a practical manifestation of Euclidean principles in the world of fashion.

Further, fabric selection is a critical step in the process. The clothier advices the client on the type of fabric that would best suit their needs, taking into account factors such as climate, occasion, and personal comfort. This is where the fundamentals of textile technology come into play, and the knowledge of fibers, their characteristics, and their influence on the final product becomes vital.

The next stage of the journey is the actual stitching of the garment. In the age of mechanization, many might assume this part of the process to be fully automated. However, in the realm of custom clothiering, a significant portion of the work is still done by hand to ensure perfect alignment and fit. In this sense, the craft of custom clothiering bridges the gap between the mass production principles of Fordism and the meticulous, labor-intensive techniques of artisanal craftsmanship.

Once the garment is assembled, it undergoes rigorous checks for fit, comfort and aesthetics in a series of fittings. Here, the clothier fine-tunes the garment, adjusting seams, letting out or taking in fabric as per the client’s feedback. The fitting stage embodies the principles of iterative design—a popular concept in the field of systems engineering and industrial design—which emphasizes the continual testing and refinement of a product until it meets the desired specifications.

Now, why would someone opt for custom clothing instead of off-the-rack options? The answer lies in the inherent human desire for exclusivity and a personalized experience. A custom-made garment, with its perfect fit and unique design, not only enhances the wearer's physical attributes but also serves as an extension of their personality. Furthermore, it fulfills the economic principle of consumer sovereignty, giving the client complete control over the product they are purchasing.

The world of custom clothiers is a fascinating blend of art and science, tradition and innovation, individuality and universal design principles. As we advance in the age of personalization, the role of custom clothiers in shaping the future of fashion becomes increasingly significant. Their ability to combine individual client preferences with universal design principles sets them apart from traditional fashion designers and retailers, making them an indispensable part of the personalized fashion ecosystem.

In conclusion, the realm of custom clothiers is a captivating intersection of fashion, art, technology, and mathematics. Its significance lies in its ode to individuality and personal expression, and its potential to redefine the future of fashion makes it a field worth watching.