word-forming element meaning "under, beneath; less, less than" (in chemistry, indicating a lesser oxidation), from Greek hypo (prep. and adverb) "under, beneath; up from under; toward and under (i.e. into)," from PIE root *upo "under."
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit gharmah "heat;" Old Persian Garmapada-, name of the fourth month, corresponding to June/July, from garma- "heat;" Hittite war- "to burn;" Armenian jerm "warm;" Greek thermos "warm;" Latin formus "warm," fornax "oven;" Old Irish fogeir "heated;" Old English bærnan "to kindle."
word-forming element in names of countries, diseases, and flowers, from Latin and Greek -ia, noun ending, in Greek especially used in forming abstract nouns (typically of feminine gender); see -a (1). The classical suffix in its usual evolution (via French -ie) comes to Modern English as -y (as in familia/family, also -logy, -graphy). Compare -cy.
In paraphernalia, Mammalia, regalia, etc. it represents Latin or Greek -a (see -a (2)), plural suffix of nouns in -ium (Latin) or -ion (Greek), with formative or euphonic -i-.
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<a href="https://www.etymonline.com/word/hypothermia">Etymology of hypothermia by etymonline</a>
Harper, D. (n.d.). Etymology of hypothermia. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/hypothermia