Julian descends from the Roman family name Julius, whose own origin is debated -- proposals range from "youthful" or "downy-bearded" to a link with Jupiter. What carries forward regardless of the exact root is an association with early promise, someone still arriving at their full shape rather than already fixed.
It behooves the astrologer to consider the time in directions of the planets; but in the fixed stars it is not so needful. - William Lilly (1602.-1681.)