Clouded is the past participle of the verb cloud, from the noun cloud, Old English clūd 'rock, hill, mass of stone' (later transferred to a cumulus mass in the sky), of uncertain further origin. The historical trail runs through clūd in Old English. The history must be left partly open, preserving the uncertainty rather than forcing a single unsupported ancestry. Used as an adjective and verb, clouded now means "darkened, obscured, or made unclear", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in related forms such as cloud, cloudy, and clouding. That uncertainty is part of the entry: the safest account is the attested form and the limited comparisons preserved with it.