pour oil on troubled waters

To calm or settle a tense situation. If those two are arguing again, send Mom in to talk to them—she's great at pouring oil on troubled waters.

Soothe or calm down something or someone, as in The twins are quarreling so I'd best go pour oil on troubled waters. This term alludes to an ancient practice of pouring oil on ocean waves to calm their turbulence, which was mentioned in the eighth century. [Mid-1800s]

If you pour oil on troubled waters, you do or say something to make people friendly again after an argument. He is an extremely experienced politician, who some diplomats believe may be able to pour oil on troubled waters. Friends are a blessing — they pour oil on troubled waters, drag you to parties and make you feel loved. Note: It has been known for a long time that pouring oil on rough water could calm it. The Greek author Plutarch mentioned it in about 95 AD: `Why does pouring oil on the sea make it still and calm?'

To soothe a turbulent situation; to calm down angry persons. This term refers to an ancient practice of pouring oil on ocean waves to decrease their violence. It was mentioned in Bede’s Ecclesiastical History (a.d. 731), which tells of an Irish monk giving a priest holy oil to pour on the sea during a storm. The term was eventually transferred to smoothing over matters of any kind. “Disraeli poured oil and calmed the waters,” reported W. B. Baring, writing about the British statesman (Croker Papers, 1847).