1. Increasing, as the light of the moon seems to increase in size during its first quarter.
2. The crescent of the moon is so called because it is increasing in size from night to night: "A crescent is used with reference to the moon in its first quarter (some dictionaries also say, the last quarter) and it is applied to anything of similar shape."

"Other things resemble the shapes of a crescent; for example, a curved pastry or the curved streets that often present a continuous façade; such as, rows of houses."

3. Etymology: from Latin crescentum, crescens from crescere, "to come forth, to spring up, to grow, to thrive, to swell, to increase in numbers or strength".