mꜣꜣt(“seeing”, feminine imperfective active participle of mꜣꜣ) + ḥr(“Horus”) + stẖ(“Set”), thus ‘(the one) seeing Horus-Set’, with ‘Horus-Set’ a reference to the king.
“mꜣꜣ.t-Ḥr.w-Stẖ (lemma ID 450539)”, in Thesaurus Linguae Aegyptiae[1], Corpus issue 18, Web app version 2.1.5, Tonio Sebastian Richter & Daniel A. Werning by order of the Berlin-Brandenburgische Akademie der Wissenschaften and Hans-Werner Fischer-Elfert & Peter Dils by order of the Sächsische Akademie der Wissenschaften zu Leipzig, 2004–26 July 2023
Jones, Dilwyn (2000) An Index of Ancient Egyptian Titles, Epithets and Phrases of the Old Kingdom (BAR International Series; 866 (I-II)), volume I-II, Oxford: Archaeopress, →ISBN, § 1562, pages 421–422
Helck, Wolfgang, Westendorf, Wolfhart (1977) Lexikon der Ägyptologie, volumes 2: Erntefest – Hordjedef, Wiesbaden: Otto Harrassowitz, page 824