Initially, stable poly-lexical units (SPUs) were denominative or connotative language units. Over time, with language evolution, some SPUs remained motivated and their components, or one of them, preserved the meaning. Other SPUs, initially motivated, became demotivated over time losing the link with the designated phenomenon. Extra-linguistic factors constitute the primary stage regarding the creation of the SPUs within the language. The motivation of some SPUs origin is explained by the foreign provenance, being borrowed, calqued or entered into language through cultural ways. In this case, they should be considered as being general for many languages. Other SPUs should be regarded as indigenous originating from the Romanian language even if they have equivalent corresponding units in other languages. As we said, initially, SPUs were denominative motivated units if they designate certain concrete facts of environment or connotative motivated units if the speaker expresses his attitude towards a concrete fact from life. Some SPUs, initially motivated, became over time demotivated, losing the incipient meaning. Firstly, it is about the phraseological units which get the complete image over time. We can distinguish two big categories of SPUs according to their origin: denominative units and connotative units. Taking into account the classification according to extra-linguistic motivation we consider important to emphasize the principle of origin: indigenous SPUs and general SPUs. The indigenous SPUs are those that belong to functional – semantic fields: everyday life, professions and occupations, fauna, military domain, nature phenomena, tabu-notions. Genreal SPUs are classified as those that entered into life through cultural way: Bible, Myths, historical realia.