to treat a dead body with spices and fragrant resins so that it will not decay: to embalm
Jacob dies in Egypt, and Joseph orders the physicians in his service to do this to his father's body. At the end of Genesis the same is done for Joseph himself. The word does not literally say "preserve" or "mummify." Its picture is spices: fragrant resins, oils, and drying salts worked into the body so that it will not rot. That is what Egyptian embalming looked like from the outside, and it is the feature this Hebrew word picks out.
Genesis also counts the treatment as a measured stretch of time. Forty days go to the body itself, while Egypt mourns for seventy. The two figures do not compete: the shorter one covers the drying and spicing, the longer one the whole official period of grief.
Two details are worth noticing. The men who do the work are called healers, the ordinary word for physicians, rather than priests, which keeps the scene clear of Egyptian temple ritual. And in both cases the point of the treatment is travel: a body that will not decay can be carried out of Egypt and buried (קָבַר) in the family grave back in Canaan.