The modern interpretation of the expression "washing the bones" means to gossip, gossip, gossip about someone. It was this form that was the basis for the formation of the word "fire", that is, "scold". However, back in the 19th century, this phrase had a completely different meaning ...
The Orthodox Greeks, as well as some Slavic peoples, had a custom of secondary burial - the bones of the deceased were seized, washed with water and wine and put back. If the corpse was found undisturbed and swollen, this meant that during his lifetime this person was a sinner and the curse lies on him - to leave the grave at night in the form of a ghoul, vampire, ghoul and destroy people.
Here is how in "History of the Russian Church" Acad. EE Golubinsky describes the custom of the Greek Church relating to the storage of the remains of people who have died: “We bury the dead in the ground and leave it in it forever. In Greece, it is not so: first, the dead are buried in the ground, and then after three years or after another certain, slightly shorter, slightly longer period, their bones are dug out of the ground and placed in a special room - kimithiria (κοιμητήριον) or tomb. The excavation and position of bones in kimithiria constitutes a special rite serving as a continuation or completion of the funeral: a priest is called and when he sings a small requiem the bones will be removed from the ground; being taken out, they are washed with water and wine, put into a small box and brought into the church, where the funeral liturgy and the great requiem are sung over them; after that they go to Kimithiry. This latter is a special house or a house or a shed at the church, in which there are, firstly, a large pit (in the middle) or a large chest for pouring the bones of poor people, and secondly, scales with boxes or shelves for the bones of rich people who want keep them separately (inscriptions are made on the turtles who they belonged to and when their owners died).
Naturally, the whole process of reburial was accompanied by memories of the deceased, an assessment of his character, actions and deeds. This was the reason for the appearance of the expression "wash the bones", which over time acquired a negative connotation.