Exceptional manners; those that are preferred or required in and among polite society. One must at all times exhibit company manners if one is to make a good impression among the more influential members of society.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
One's best behavior, as in George never interrupts when we have guests; he has fine company manners. This term employs company in the sense of "guests." An older variant, Tell me thy company and I'll tell thee thy manners, uses company in the sense of "companions." The current term implies that one is more mindful of politeness with invited guests.
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.