palm oil

In the sense of a bribe, the phrase is a punning reference to the palm of the hand.

palm oil (countable and uncountable, plural palm oils)

1. An edible plant oil derived from the mesocarp (reddish pulp) of the fruit of the oil palm (Elaeis guineensis).
   • 2013 June 29, “Unspontaneous combustion”, in The Economist, volume 407, number 8842, page 29:

     Since the mid-1980s, when Indonesia first began to clear its bountiful forests on an industrial scale in favour of lucrative palm-oil plantations, “haze” has become an almost annual occurrence in South-East Asia.

2. (slang) Money given as a bribe.

The oil palm tree also yields a different type of oil from its kernel. This is known as palm kernel oil.

• oil lamp, oil palm, oilpalm