In this paper, it is about demonstrating that in a rather significant number of triliterals roots ending with ʿayn, analyzed and commented case by case, this final segment is correlated with the notion of « intensiveness » . The roots in question are thus submorphemically analyzed in a biliteral basis {R1R2} followed by a submorphemic suffix /ʿ/ related to the notion of intensivity. From a theoretical point of view, and from the side of the Arabic grammatical tradition, we discuss Ibn Ğinnî's reflections on the subject of the sound-meaning relationship, and on the side of modern linguistics, we rely on the work of Pierre Guiraud on onomatopoeias in order to motivate the phono-semantic correlation between the sound /ʿ/ and the notion of « intensiveness »: the sound /ʿ/ would be considred as the articulatory realization of the idea of « intensivity » in the Arabic lexicon. Keywords: triliteral root, bilitarism, etymon, submorpheme, submorphemic suffix, intensive, motivation, phono-semantic correlation, articulatory onomatopoeia, acoustic onomatopoeia.