the longest words (and that isn't the longest) are also more known than other uncommon words by the simple facts they're long
scientific words are also generally disqualifying because they're technically assembled from combining forms and you can theoretically make an infinitely long word using recursive combining forms to describe some hypothetically infinitely regressive condition
The longest word in any of the major English language dictionaries is pneumonoultramicroscopicsilicovolcanoconiosis, a word that refers to a lung disease contracted from the inhalation of very fine silica particles, specifically from a volcano; medically, it is the same as silicosis.
the Ch'eng-Chu school (of thought) is neo-confucianist philosophy, not "school of law," and isn't a word but two hyphenated names (Ch'eng, from Ch'eng Hao and Ch'eng I; and Chu Hsi) and a descriptive noun (school)
Ch'eng-Chu (the school of thought) and school (describing aforementioned school) are two distinct words, one being a proper noun and one being a regular noun
