know which side one's bread is buttered on

present singular third person knows which side one's bread is buttered on · participle present knowing which side one's bread is buttered on · past knew which side one's bread was buttered on · past knew which side one's bread is buttered on · participle past known which side one's bread was buttered on · participle past known which side one's bread is buttered on · alternative know on what side one's bread is buttered · alternative know on which side one's bread is buttered · alternative know what side one's bread is buttered on · alternative know what side of one's bread is buttered · alternative know what side of the bread is buttered · alternative know which side of one's bread is buttered · alternative know which side of the bread is buttered

1. idiomaticTo be aware of where one's interests lie in a situation.

   He knows which side his bread is buttered on through in all probability he never realised what it is to be without regular meals.

   1922 February 2, James Joyce, “[Episode 16: Eumaeus]”, in Ulysses, Paris: Shakespeare and Company […], →OCLC, part III [Nostos], page 576

   2 more examples

   They are all stupid when they are not crafty, and very few of them are crafty. The only wise Republicans are the millionnaires and their conscious henchmen. They know which side their bread is buttered on, and they know why.

   1908 September – 1909 September, Jack London, chapter XXIX, in Martin Eden, New York, N.Y.: The Macmillan Company, published September 1909, →OCLC, page 258

   Many of them must have agreed in their hearts, and applauded his courage secretly. But their foolishness was of the world; they knew which side their bread is buttered on.

   1955 November, “Mississippi Loses a Minister”, in Clair M. Cook, editor, Economic Justice […], volume XXIV, number 3, Columbus, Oh.: National Religion and Labor Foundation, →OCLC, page 5, column 2