We already read in Old Kingdom how Isis and Nephtys were considered the responsible ones of the dead resurrection: “Ounas goes up through the two thighs of Isis. Ounas rises through the two thighs of Nepthys” [1]. Both goddesses were the two women who conceived and who gave birth to the Pharaoh, this one rose to heaven after his night travel (death). In the funerary context, the dead Osiris had to be reborn as the son of Geb and Nut: “he is the first-born of Geb, the first-born son of Nut, the one who gone out from the womb with the ureus…”[2]. Also, the resurrection of the deceased had a lunar nature and there is another explanation of the lunar cycle, in which the star was born from the womb of the sky goddess Nut and was then swallowed by her at the end of the cycle[3]. Taking into consideration these three points, we could consider that the two women representing Isis and Nephtys in the symbolic sphere engendered the newborn (the dead) and in somehow made also the role of mothers of the deceased. For that reason we read in the Pyramid Texts “Isis has conceived him and Nephtys has nursed him” [4]. From the Old Kingdom there was a relationship between the goddess Nut and the hair: « Nut gives you her two arms, she with the long hair, whose breasts are suspended »[5]. 
Also in the Middle and the New Kingdoms we read: “…this N. goes up to Busiris for seeing Osiris… Nut shakes her hair when she sees me…”[6] So, from those quotes we could imagine the goddess Nut making the nwn gesture of shaking hair onwards. The following step was to search on the multiples images in Ancient Egyptian art of Nut and to see if that could have an iconographical basis. The best example is the funerary stele of the Lady Taperet from XXII Dynasty. It is a small wooden stele with painted decoration in both sides with Taperet praying Ra and Atum. On both sides the upper part is decorated with the body of Nut as the vault of heaven, interesting is the scene with Atum where Nut is the firmament and her hair is falling onwards.
Funerary stele of Lady Taperet with an image of Nut in nwn gesture. XXII Dynasty. Musée du Louvre. Photo: http://www.nybooks.com
This image of Nut and the fact that she is the mother of Osiris in the Ancient Egyptian cosmogony lead us to the conclusion that passages from Pyramid Texts, Coffin Texts and Book of the Dead allude to the birth of the dead. Nut, bended and with her face looking at her pubis sees how his son (the dead) is coming to life. For that reason it is said that Nut shakes her hair when she sees Osiris; in that moment she is making the nwn gesture. This posture has then a very strong symbolic meaning: it is an image of maternity and very close to the rebirth of Osiris as a newborn/resurrected. There is also similar example in a coffin of Uresh-Unefer from the Late Period. We see in it a relief with late version of the same scene with Nut onwards and with a suspended lock of hair. Thinking about coffin as the receptacle of the mummy we need to look on how could be Nut represented on it.
Relief on the coffin of Uresh-Nefer. Late Period. Metropolitan Museum of New York. Photo: http://www.egiptologia.net
There are many examples of coffins from the Late Period with representations of Nut on the internal side of the cover. In them the goddess is frontally extended all over the surface with hair standing up. In this case we are facing just a different perspective of the same posture. Nut in the cover would be making also the nwn gesture of shaking the hair onwards. The goddess as the sky vault swallows the evening sun and gives birth the morning sun; also many times Nut is the night sky, so she swallows the evening sun and gives birth the full moon.
Coffin of Khenstefnakht from the Late Period. Inside the cover, the goddess Nut with her hair standing up. She swallows the evening sun and gives birth the morning sun. Musée Royaux d’Art et d’Histoire (Brussels). Photo: http://www.vroma.org
Internal side of the cover of the Coffin of Peftjauneith. Nut in black is an image of the night sky vault. The goddess with her mane standing up is swallowing the evening sun and giving birth the full moon. Rijsmuseum. Photo: http://www.rmo.nl
Inside the coffin takes place the conception and rebirth of the dead, Nut bended, with the hair onwards, will give birth his son Osiris and will put her arms around him: “…Geb is there protecting you; he is your father, you have been put on the world by him; the arms of Nut are around you, she has brought you to life, she brings your beauty…”[7].
HAIR AND DEATH IN ANCIENT EGYPT 