English

isobase

From iso- + base?

Formed from iso- + base

Ancient Greek ἴσος ‘equal’

English iso-

Proto-Indo-European *gʷem- ‘to come’

…

Ancient Greek βᾰ́σῐς ‘stepping’

Latin basis ‘a pedestal’

Old French base

Middle English base ‘a foundation or base’

English base

Today it means

noun A line drawn on a map or chart connecting places of equal or constant land upheaval or subsidence.

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