and Nakir, according to Mahometan mythology, are two angels who interrogate the dead immediately they are buried. The first two questions they ask are, “Who is your Lord?” and “Who is your prophet?” Their voices are like thunder, their aspects hideous, and those not approved of they lash into perdition with whips half-iron and half-flame. (See Munkar.)
“Do you not see those spectres that are stirring the burning coals? They are Monkir and Nakir.” —Beckford; Vathek.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894