Also, oil someone's palm or hand. Give someone money in exchange for a favor; also, bribe someone. For example, If you want you luggage to make the plane, be sure to grease the porter's palm. This term uses grease in the sense of "enrich." [First half of 1500s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. All rights reserved.