English word semester comes from Latin sex ((cardinal) six; 6.), Latin mensis (Month.)
sex (Latin)
(cardinal) six; 6.
mensis (Latin)
Month.
sēmestris (New Latin)
semestris (Latin)
Semester (German)
Semester.
semester (English)
A period or term of six months.. Half of a school year (US) or academic year such as fall or spring semester.