Exodus 13:4 - Ellicott's Commentary On The Whole Bible

The month Abib. — Abib means “green ears of corn,” or “greenness;” and the month of Abib was that in which the wheat came into ear, and the earth generally renewed its verdure. It was a “vague,” or shifting month, since it properly began with the day of the full moon that followed next after the vernal equinox. It retained its name until the Babylonian captivity, when the Babylonian name Nisan superseded the original one (Nehemiah 2:1; Esther 3:7).