The term prosaic comes from the late Latin " prosaĭcus ", and was used to refer to something relative or belonging to the prose, or that contained it.
From this point of view, the concept could be related to practicality, pragmatism or utility, and be associated with that which lacks a high, abstract or symbolic claim.
Something prosáico connotes to have characteristics of prose or that, in a certain way, belongs to it to a greater or lesser degree. For example, writing prose becomes prosaic writing.
In this way, the etymological concept of this word can be considered the relative or belonging to the prose or that contains it.
In Ancient Rome, poets were very rigorous in poetic construction: they used rhyme, a certain number of syllables for each verse, and certain verses for each poem. But this was modified by a new poetry in the form of prose, in this way it was called prosaic in the sense of low, rude and vulgar.
In colloquial speech it is understood that someone uses prosaic language when describing the world and events in a rational way. For example, if you want to define love and talk about chemical reactions and biology, you will develop a prosaic definition. If, instead, it is based on the fusion of souls and develops the subject from an abstract perspective, it will use a poetic language.
Synonyms of the word prosaic: practical, pragmatic, material; trite, pedestrian, mediocre, rude, trivial, vulgar, common; friendly.