I believe this is a reference to the following quote by Galileo: "Mathematics is the language with which God wrote the universe.".
If a physicist or mathematician talks about god with reference to physics or maths, they tend to use the term as a shorthand for "nature", or "the laws of the universe". Thus when Einstein says "God does not play dice with the universe", it's a figure of speech: he's really talking about the laws of nature, not a religious entity as such.
This type of God is often referred to as "the God of Spinoza", a 17th century Dutch philosopher, who put forward the idea that God is the universe and its laws, rather than an anthropomorphic entity existing outside the universe. Spinoza's "God" can be interchanged with such terms as "the cosmos" or "nature", both of which are defined (as far as we can tell) in mathematical terms.
Einstein himself agreed: “I believe in Spinoza's God, who reveals Himself in the lawful harmony of the world, not in a God who concerns Himself with the fate and the doings of mankind... "
Therefore, the quote from Galileo, which your question echoes, can be interpreted as support for "the god of Spinoza", (even though Spinoza came after Galileo) and since this is a commonly used term within scientific/philosopical discussion about God, you could just stick with that rather than invent something new.
Wikipedia has a page on "Spinozism", so I suppose a person following this could be called a Spinozist. https://en.wikipedia.org/wiki/Spinozism
And, in fact, from that same Wikipedia page: "In 1785, Friedrich Heinrich Jacobi published a condemnation of Spinoza's pantheism, after Lessing was thought to have confessed on his deathbed to being a "Spinozist", which was the equivalent in his time of being called a heretic. "