L. Dow Balliett published a series of books from the turn of the twentieth century on what she called the vibration of numbers and of names, in the general New Thought idiom of the period, in which a name and a birth date were held to carry a character that could be read off. Her material was suggestive rather than systematic: it asserted correspondences without laying down a single procedure that two practitioners would follow identically.
The Institute, founded in California in 1931, is where the procedure was laid down. Juno Jordan, who had studied with Balliett, led it for decades, and its publications and courses fixed the elements that modern English language numerology now treats as given: the assignment of the numbers one to nine to the letters of the Latin alphabet in order, the rule that a total is reduced by adding its digits until a single figure remains, the exemption of the master numbers eleven and twenty-two from that reduction, and the standard set of readings calculated from a birth date and a birth name.
Those calculations, the life path from the date, the expression from the full name, the soul urge from its vowels and the personality from its consonants, are the ordinary furniture of numerology as it is taught and sold today, and they were standardised here rather than inherited from anywhere older.