Emptiness: black 37%, grey 21%, white 21%, …
Heller (1989)

In the vicinity of most Russian cities, large, open pits were dug into which the corpses of the murdered, drowned, suicides, etc. were thrown. These pits were only filled in after Easter. The people called such a pit ‘ubogij dom’ (house of the poor). This term means in Old Russian, as in practically all Slavic languages: “poor, needy.” It is a derivation consisting of the prefix u-: ‘away, down’ and the stem ‘bog’. So the original meaning is: ‘without bog’, i.e. ‘who has been deprived of his share of prosperity and fortune’, hence ‘poor, who knows no wealth’ and especially ‘dead, who has been deprived of his share in life’. Therefore, the pit of the violent dead was called “uboji dom”, i.e. “house of the dead or poor.”

(Vyncke, 1969)