Hi, Rusty!
Now, oil on troubled waters......
My 'old' Brewers strangely enough offers answers......it isn't in my 'new' one! (another reason for maybe keeping both volumes?)
There is too much to include it all, but briefly....."To pour oil on troubled waters "is to soothe the troubled spirit."
The origin of the phrase is mentioned by the Venerable Bede (you mentioned him?).
St Aidan gave his blessing to a young priest who was to set out by land , but return by water, to convoy a young maiden to be the bride of King Oswin or Oswy.
St Aidan gave the young man a cruse of oil to pour on the sea if the waves became stormy.
A storm did arise, and the young priest ,by pouring oil on the waves, did in fact reduce them to a calm.
Bede says that he had this story from "a most creditable man in Holy Orders."
But St. Aidan died in 694, and Bede died in 735??!
You also mentioned Pliny? Where does he fit in?