Why is the ‘p’ in ‘pH value’ in lowercase, while ‘H’ is uppercase?

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“In “pH”, the “H” stands for hydrogen ion, H+, and this is beyond doubt; however, the origin of the ‘p’ value is subject to debate. 1 The first term, p, represents the German word “Potenz,” which means strength or intensity; it is also said to represent the French word puissance, which likewise means strength or intensity ； 2 The second term, pH, comes from the Latin word “pondus hydrogenii”, which means “quantity of hydrogen”. Another theory is that it derives from the Latin word “potentia hydrogenii” (capacity of hydrogen), corresponding to the English term ‘potential hydrogen’. 3 The third view is that p is merely a symbol arbitrarily chosen by the proponent Sorensen, since he also used q. 4 In modern chemistry, the symbol p is used in front of dimensionless quantities to denote the negative logarithm of that quantity; therefore, p should be written in lowercase. H represents a hydrogen ion; since the element symbol for hydrogen is H, it must be written in uppercase!