Heru-ra-ha combines the ideas of Horus (cf. also 'the great angel Hru' who is set over the Book of Tahuti; see Liber LXXVIII) with those of Ra and Spirit. For He-Aleph is the Atziluthic or archetypal spelling of He, the Holy Ghost. And Ha=6, the number of the Sun. He is also Nuith, H being Her letter.
The language suggests that Heru-Ra-Ha is the 'true Name' of the Unity who is symbolized by the Twins Harpocrates and Horus. Note that the Twin Sign -- and the Child Sign -- is Gemini, whose letter is Zain, a sword.
The doctrine of the dual character of the God is very important to a proper understanding of Him. "The Sign of the Enterer is always to be followed immediately by the Sign of Silence": such is the imperative injunction to the Neophyte. In Book 4 the necessity for this is explained fully.