Pentru multe expresii ce au o existenţă îndelungată în limbă (uneori de-a lungul veacurilor), acumularea în structura lor a diverselor tipuri de arhaisme devine un indiciu al frazeologizării lor, precum şi un criteriu ce ar permite distingerea acestora de îmbinările libere de cuvinte. Prezenţa elementelor arhaice, deşi contribuie la solidificarea relaţiilor de structură în cadrul îmbinărilor stabile de cuvinte, nu explică motivele apariţiei frazeologismelor. Mai degrabă, ele reprezintă o mărturie că această îmbinare a devenit una stabilă de mult, că elementele ei componente au reuşit „să se învechească” şi „să rămână în urma” evoluţiei sistemului lexical, fonetic sau gramatical.

Characteristic feature of phraseological units is that just like language in general, they are in a perpetual evolution, which involves, in some cases, preserving some archaic elements in their structure. However, the tendency to substitute/ „upgrade” the archaisms that are component parts of phraseological units is rather intense. Conclusive evidence in this regard are the phraseological units in which the archaic element was replaced by its newer synonym, which, as a consequence of competition, removed the former from circulation. The fact that the lexical system of a language influences the structure of phraseological units serves as evidence that the component elements of phraseological units (including phraseological units that contain archaic elements) maintain their ties with the lexical system, and through it, with the grammatical, phonetic, derivative system as well. Thus, there is a certain revitalization of canonic phrases by circumscribing them in the same significance area without producing an essential value mutation.