A most notable feature of Standard Modern Greek (SMG) lexicon is the abundance of pairs of lexemes of similar meaning which belong to different registers. Thus, while one lexeme pertains to the colloquial language and is widely used both in oral and written speech, a semantically akin or even synonymous word of Ancient (i.e., Classical) Greek (AG) origin is also attested in specific contexts. The latter ones are usually described as part of the “archaic” or “learned” component of the Modern Greek (MG) lexicon. In the light of three case studies, our paper aims at investigating this variation by conducting research through diachronic corpora. We intend to disperse certain misconceptions concerning lexical change (which is erroneously interpreted as a straightforward replacement of an “older” word with a new one) and to introduce the concepts of adstratal and superstratal lexicon along with the theory of prototypicality and exaptation in the relevant research. Along with dealing with the diachrony of the Greek lexicon, our account sketches a first theoretical framework for investigating the lexicon of languages with a long-recorded history and diglossic contradictions. Accordingly, it emphasizes the vital role of corpora research in diachronic semantics and onomasiology