[Mesorah] "Vayigva Yitzchok vayomos vayeosef el amov"

[Dov Bloom]

If have no sources, but "vayeosef el amov" always sounded to me like it refers to something *after* death, perhaps relating to the funeral and/or burial. (Akiva Miller)

Acc'd to the moderns, vayeosef el amov - He was buried in the family burial plot. (literally came from the idea of likut atzamot, for a year the body decomposed, and after a year all the bones were put in a family pile? 
There are many halachot about likut atzamot, being another day of aveilut