Pneumonoultramicroscopicsilicovolcaniconiosis is English, but it is a medical word. The roots of it are Greek and Latin, like much of English. Are you aware of the etymology of antidisestablishmentarianism?

In English, I understand it to be pneumonoultramicropicsilicovolcaniconiosis, although I may have misspelled it from memory. It’s a medical condition resulting from inhaling fine particles of silica.