⚫️Japanese onomatopoeia Vol. 32 “MOKUMOKU”（モクモク）by Kay Koyama (JPN)
“MoKUMOKU” is sometimes expressed with Chinese characters of “Silent（黙）”, but as an onomatopoeia, I think, means “Piling visible but uncatchable gas or clouds.
★雲がもくもく、発達している。KUMO GA MOKUMOKU HATTATSU SHITEIRU. → The clouds’ growing.
★タバコの煙が部屋にもくもく充満している。The room is filled with people’s cigarette smoke.