The Greek noun basanos originally referred to a touchstone — the black stone used to test the purity of gold by the mark it left. From this it developed the meaning of torture or torment (the test by pain). In the New Testament it appears in Matthew 4:24 (various diseases and pain) and in the parable of the rich man and Lazarus (Luke 16:23,28) where it describes the torment of Hades.
The metaphorical background of basanos as a testing stone is theologically suggestive: just as gold is tested by the stone, character is revealed and purified through suffering. James 1 and 1 Peter 1 develop this idea — trials test and refine faith as fire refines gold. However, the Lukan use in the Lazarus parable takes the word in its darker sense: the rich man in Hades was in agony, a sobering reminder that the choices of this life have eternal weight.