o-le-ag-i-nous / ō-lē-ăj-ə-nəs
1. pertaining to oil; oily
The gems cling to the oleaginous substance.
From “An African Adventure” by Isaac F. Marcosson, 1877 – 1961
2. overly smug or ingratiating; unctuous
The man of law consoled him with oleaginous phrases: told him he very much underrated the power of money.
From “White Lies” by Charles Reade, 1814 – 1884
From the Latin adjective oleaginus (of the olive-tree [olea]) through the French adjecitve oleagineux (oily, unctuous).
Thank you to Allen Ward for providing this etymology.