Read through the whole article on Wikipedia (https://en.wikipedia.org/wiki/Moore%27s_law), but I can't find anything about why it was called a law when it is described as a prediction or an observation. Is it an incorrect usage of the word, can we claim something to be a law just for the heck of it in philosophy? I am thinking this is in the realm of philosophy since it cannot be considered to be computer science to ponder about the raison-d'etre of a terminology or its justification. Can we call any speculative observation to be a law, or is there some kind of rule to this madness?
Per Conifold's comment, Moore's Law is an empirical law based on observation; it is not a physical law like Maxwell's equations or Einstein's law of general relativity or the Carnot efficiency of a thermodynamic process.
Moore's law was driven by two trends in the technology of integrated circuit manufacture: 1) that defect densities will go down as mastery of the technology is achieved, and 2) that feature sizes will decrease with advances in that technology.
These two things allow the manufacture of ever-larger chips without yield losses, with ever-denser transistor packing on each one. The net result of these two things is what was called "Moore's Law".