Thermo is a loan word that people hispanize as "termo" (the Spanish equivalent).

well, thermo is from the greek word thérmē meaning heat. we use the termo- suffix for all things that involve heat (thermodynamics -> termodinámica, thermometer -> termómetro)

Prefix. Suffixes come at the end.

I am aware of the etymology you refer to, but in this case I am referring to something different.

The noun "termo" in Spanish is formally recognized by the RAE to refer to a vacuum insulated food jar (such as the ones sold by Thermos®), and that is the word I was referring to, as it is the most widely identifiable use of the word "termo" in Spanish.

https://dle.rae.es/termo

i.e.: "Pasame ese termo por favor?", "Se me ha quedado el termo en mi casa".

Yeah, and "litho" is also a Greek root than in Spanish is written "lito": https://dle.rae.es/lito-#NRayp6C