- quiet, quietenAs a verb, quiet has been used transitively (with an object) since the 16c in the meaning ‘to make (someone or something) quiet’, and is still in use in this sense:
• The unexpectedness of this departure from the routine at first disquieted but then quieted us all —M. Lindvall, 1991.Since the 18c, and especially in North America, it has also been used intransitively (often in extended meanings to do more with disposition and temperament than actual sound):
• When I switched to opiates at least I quieted down —New Yorker, 1992.The alternative verb quieten appeared (often with down) in the 19c in both transitive and intransitive uses; because quiet was available, it was regarded by Fowler (1926) as a ‘superfluous word’, but in more recent usage the stigma has mostly disappeared, leaving quieten now the more common choice than quiet:
• The youth…revved the engine, then quietened it down to the soft ticking-over —J. Wainwright, 1973
• Arnica also helps to calm and quieten the upset child —Health Shopper, 1990————————
• It's not so much that I've quietened down, as that I've channelled my energies into things that are more productive than out-and-out hedonism —Female First Online, BrE 2005 [OEC].quiet, quietness, quietudeThe most commonly used of these nouns is quiet, which denotes a state of silence or tranquillity (the quiet that precedes a storm / a period of peace and quiet). Quietness also has this meaning but tends to denote rather the condition of being quiet as applied in a particular instance
• (I like to leave the noise of the discos and bars behind me and return to the quietness of my home for a good night's sleep —Pattaya Mail, 2004)and quietude is a literary alternative for quietness
• (Their two and one-half acres retain a bucolic quietude —Angeles, AmE 1991).
Modern English usage. 2014.