The Secret One, The Inner One, The Intimate.
Allah is Al-Baatin سُبْحَٰنَهُۥ وَتَعَٰلَىٰ (in Arabic: ٱلْبَاطِنُ), The One who is hidden or secret. Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ is unseen but His existence is known through signs. Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ immanent operating within all of creation. The one who is the secret inner companion.