Толковый словарь английского языка Oxford English Reference - ous

suffix. 1 forming adjectives meaning 'abounding in, characterized by, of the nature of' (envious; glorious; mountainous; poisonous). 2 Chem. denoting a state of lower valence than the corresponding word in -ic (ferrous). Derivatives -ously suffix forming adverbs. -ousness suffix forming nouns. Etymology: from or after AF -ous, OF -eus, f. L -osus