disapproval If you describe someone as po-faced, you think that they are being unnecessarily serious about something. Coltrane took a rather po-faced view of this. having an unfriendly disapproving expression on your face (Perhaps from po (19-20 centuries), from pot, influenced by poker-faced)
() Probably from po, abbreviated slang based on French pot de chambre (chamber pot), after the distasteful expression anyone would adopt upon being presented with a full one. Perhaps similarly from pooh; perhaps influenced by poker-faced. Also possibly “poor-faced”.