Generally taken to represent a hemispherical loaf of bread, with the phonogrammatic value t deriving by rebus principle from its use as a logogram for t(“bread”). This glyph was conventionally colored black or blue, like 𓏙
(generally interpreted as a conical bread loaf), but comparing those to 𓏐
where bread is yellow, Nunn writes that the black/blue coloration raises questions about their identification as bread. He notes that 𓉞
and similar glyphs have this glyph at the center, and because temples were symbolically built on "the primaeval mound of creation", black and blue could represent mud there and this could "explain why this 'loaf' X1 is always painted black or blue, even [...] in words for bread, where these colours seem out of place".
Gardiner, Alan (1957) Egyptian Grammar: Being an Introduction to the Study of Hieroglyphs, third edition, Oxford: Griffith Institute, →ISBN, page 531
Henry George Fischer (1988) Ancient Egyptian Calligraphy: A Beginner’s Guide to Writing Hieroglyphs, New York: Metropolitan Museum of Art, →ISBN, page 14
Betrò, Maria Carmela (1995) Geroglifici: 580 Segni per Capire l'Antico Egitto, Milan: Arnoldo Mondadori Editore S.p.A., →ISBN
Peust, Carsten (1999) Egyptian Phonology: An Introduction to the Phonology of a Dead Language[1], Göttingen: Peust und Gutschmidt Verlag GbR, page 48
David Nunn, A Palaeography of Polychrome Hieroglyphs (2020): "why, if X1 represents a loaf, is it consistently coloured black or blue? These are colours used to represent the Nile flood, alluvium, [...] but not, it would seem from the signs X2 - X6, bread. Takács (1996) sees a relationship, supported by many Afro-Asian cognates, between the verb tA “to bake, be hot, burn” (Wb V, 229) and the substantive t “bread”. This would fit the colour of X1 but would still not explain why X2-X6 are coloured differently. Tiradritti (2008, 6) proposes to see in X1 the representation of the primeval mound of earth that rose from the Nun at the Creation. This is a clear possibility as blue-black is the colour used to represent the fertile land that borders the Nile. The sign can also be found in some composite hieroglyphs such as the temple enclosure O7 or the symbol of the West R13. In the case of O7, temples were supposedly built on the symbolic primeval mound. This would explain the X1 sign in the centre of the enclosure."
