Here's a breakdown of its likely development:
* Physical analogy: The word "belt" is associated with physical exertion and force, as in "belting out a punch" or "belting out a laugh." This connection is reinforced by the image of singers using their diaphragm and chest muscles to project their voice powerfully.
* Musical connotation: The word "belt" started being applied to singing in the late 19th and early 20th centuries, likely influenced by the rise of opera and musical theater, where singers were expected to project their voices with impressive volume and power.
* Evolution of meaning: The phrase "belt out" eventually came to describe any type of singing done with strong force and energy, regardless of the genre. It can be used for everything from rock anthems to operatic arias.
Therefore, "belt out" likely emerged from a combination of the physical act of singing with force and the cultural association of powerful vocal delivery, particularly in genres like opera. It captures the image of a singer putting all their energy into their performance.