Why is the ninth month called September?
1650s, of diseases, etc., from Latin eruptus, past participle of erumpere "to break out, burst" (see eruption). Of volcanoes, from 1770. Related: Erupted; erupting.
erupt e·rupt (ĭ-rŭpt')v. e·rupt·ed, e·rupt·ing, e·rupts
To break through the gums in developing. Used of teeth.
To appear on the skin. Used of a rash or blemish.