Discuss sardonic here.
adjective
1) Apparently, but not really, proceeding from gaiety or mirth; forced. (Said of a laugh or smile.)
“Where strained sardonic smiles are closing still.” - Reliquiae Wottonianar
2) Bitterly ironical; sarcastic; derisive and malignant.
“A broad sardonic smile
Of dread significance.” - Cowper
[French sardonique, from Latin sardonius; Greek sardonios, sardanios, whence sardanion gelan = to laugh bitterly or grimly, probably from sairo = to draw back the lips and show the teeth, to grin; by some derived from sardonian, a plant of Sardinia, said to screw up the face of the eater.]
