ōs- / Indo-European roots
Examples of words with the root ōs-: Auriga, inosculate, oral, orifice, oronasal, orotund, os, oscillate, oscitancy, osculate, osculum, ostiary, ostium, usher.
Mouth.Oldest form *h3ōs-, but precise preform uncertain.
1. oral, os1, oscillate, osculate, osculum, ostiary, ostium, usher; inosculate, orifice, oronasal, orotund, oscitancy, peroral from Latin ōs (stem ōr-), mouth, face, orifice, and derivative ōstium (< suffixed form *ōs-to-), door.
2. Auriga from Latin aurīga, charioteer (< *ōr-īg- "he who manages the (horse's) bit";-īg- lengthened from ig- driving, from *ag-; see ag-) possibly from ōs-
[Pokorny 1. ōus- 784.]