悶聲發大財

to amass wealth while keeping a low profile (idiom)

stuffy / shut indoors / to smother / to cover tightly

bored / depressed / melancholy / sealed / airtight / tightly closed

sound / voice / tone / noise / reputation / classifier for sounds

to send out / to show (one's feeling) / to issue / to develop / to make a bundle of money / classifier for gunshots (rounds)

see 大夫[dai4 fu5]

big; large; great / older (than another person) / eldest (as in 大姐[da4 jie3]) / greatly; freely; fully / (dialect) father / (dialect) uncle (father's brother)

money / wealth / riches / property / valuables