Is the science of names and numbers real, and are there letters of ill omen and letters of good fortune? If so, how is the appropriate name for a newborn calculated, and is the name "Haya" suitable despite its absence from dictionaries?

The assertion that letters are divided into auspicious and inauspicious is without proof, and it stems from magic and sorcery, which are blameworthy in Islamic law. It has been reported from Ibn Abbas that whoever calculates using abjad numerals and gazes at the stars will have no share (reward) with Allah. Learning abjad letters with the claim of knowing the unseen is called "Ilm al-Huruf" (the science of letters), and it is among the forbidden innovations. As for using letters to determine "the lucky name," it is among the forbidden superstitions that a Muslim must avoid. There is no religious impediment to naming a girl "Haya" because it is a vocative particle.