before vowels om-, word-forming element meaning "raw, unripe," from Greek omo-, comb. form of omos "raw," from PIE root *omo- (cf. Sanskrit amah "raw, uncooked, unripe," Old Irish om, Welsh of).
Online Etymology Dictionary, © 2010 Douglas Harper
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.