For questions of linguistic etymology, I like to check out an etymology dictionary. I have found etymonline.org to have a good online etymology dictionary.

Their entry for pi notes that:

As the name of the mathematical constant, from 1841 in English, used in Latin 1748 by Swiss mathematician Leonhart Euler (1707-1783), as an abbreviation of Greek periphereia "periphery."

Now, let's look at the entry for pie, which they trace as early as 14th century English, derived from latin.

So no, the etymologies are unrelated, and Pi as a mathematical term is actually more recent.