Literally: to look at each other like earthenware dogs.
Meaning: to look at each other coldly, to glare at each other.
Origins: End of the 17th century, when the fireplace was the only source of heat in a house, people gather around the foyer in the evening. It was not uncommon to display ornaments on the mantel. Those objects very often made of Faience and often represented dogs, placed symmetrically on the mantel and seemed to glare at each other’s.
Example: “ Il me regardait en chien de faïence sans aucune raison apparente.”
Faience is a glazed ceramic ware, in particular decorated tin-glazed earthenware of the type which includes delftware and maiolica.