Why is the ninth month called September?
"to come into flower," 1775, from Latin efflorescere "to blossom, spring up, flourish, abound," from ex "out" (see ex-) + florescere "to blossom," from flos (see flora).
effloresce ef·flo·resce (ěf'lə-rěs')v. ef·flo·resced, ef·flo·resc·ing, ef·flo·resc·es
To blossom; bloom.
To become a powder by losing water of crystallization, as when a hydrated crystal is exposed to air.