Semester

The word semester, from 1827, comes from German Semester, meaning a half-year or six-month course at a university.
 
The word semester has its origins in Latin mensis (month) which in turn comes from Proto-Indo-European (PIE) me(n)ses (moon, month).
 
So, what is six months in Latin? Latin sex (six) + mensis = semenstris, semestris (of six months, lasting six months, half-yearly, semi-annual). In other words, semester.
 
Reference: Online Etymological Dictionary, https://www.etymonline.com/
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