English

hemimeridian

From hemi- + meridian.

Proto-Indo-European *sem- ‘one, whole’

Proto-Indo-European *sēmi ‘half’

English hemi-

Proto-Indo-European *dyew- ‘sky, heaven’

…

Latin medīdiēs

Latin merīdiēs ‘midday, noon’

Latin merīdiānus ‘midday, noon’

Middle English meridian

Today it means

noun Either half of the curved surface of a cornea

Language periods are conventional ranges, not dates for this word.

Etymograph / hemimeridian