SUBSTRATUM
substrate, substratum
(noun) an indigenous language that contributes features to the language of an invading people who impose their language on the indigenous population; “the Celtic languages of Britain are a substrate for English”
substrate, substratum
(noun) any stratum or layer lying underneath another
substrate, substratum
(noun) a surface on which an organism grows or is attached; “the gardener talked about the proper substrate for acid-loving plants”
Source: WordNet® 3.1
Etymology
Noun
substratum (plural substrata)
A layer that lies underneath another.
Synonym: underlayer
(figuratively) The underlying cause or basis of something.
(linguistics) A substrate.
Source: Wiktionary
Sub*stra"tum, n.; pl. Substrata. Etym: [L. substratus, p.p. of
substernere to strew under; sub under + sternere to strew. See
Stratum.]
1. That which is laid or spread under; that which underlies
something, as a layer of earth lying under another; specifically
(Agric.), the subsoil.
2. (Metaph.)
Definition: The permanent subject of qualities or cause of phenomena;
substance.
Source: Webster’s Unabridged Dictionary 1913 Edition