Natalie Portman's Baby Name Revealed

07/06/2011 at 03:00 PM EDT

Natalie Portman and fiancé Benjamin Millepied get an A-plus for the name they picked for their baby boy.

Their son's name is Aleph, a source confirms to PEOPLE.

So what's in a name? Aleph is the first letter of the Hebrew alphabet, much like alpha is the first letter of the Greek alphabet. Aleph is the number 1 in Hebrew and can also be spelled "alef."

Its esoteric meaning in Judaic Kabbalah, as denoted in the theological treaty Sefer-ha-Bahir, relates to the origin of the universe, the "primordial one that contains all numbers."

PHOTOS: Natalie Portman's Red Carpet Bump Style

Portman, 30, met choreographer Millepied on the set of Black Swan, for which she later won an Oscar for Best Actress.

• Reporting by JOEY BARTOLOMEO