monimolimnion
The lower, dense stratum of a meromictic lake (one with permanently stratified layers) that does not mix with the waters above.
Mermomictic^([sic – meaning meromictic]) lakes may have an extremely high calcium carbonate content in the monimolimnion.
Where it comes from
From Ancient Greek μόνιμος (mónimos, “stable, permanent”) + -limnion (from Ancient Greek λῐ́μνη (lĭ́mnē, “lake”) + -ion), first appearing in the writings of British ecologist George Evelyn Hutchinson (1903–1991).
Adapted from the Wiktionary entry monimolimnion (CC BY-SA 4.0).