Knowledge about phonaesthesia has particularly been deepened since 1930 until now. Starting from John Wallis’ first thoughts on the subject in 1653 via the contributions from John Rupert Firth’s post-1930s’ studies, the phenomenon has seen a growing interest as the result of the consolidated – but still to some extent arbitrary – interactions between meaning and sound over time. This paper focuses on some relevant issues in the field of diachronic linguistics, especially in connection with etymological reconstruction, to evaluate phenomena that, in a certain sense, appear to be correlated with the idea of a posteriori re-motivation by the speaker, investigating phonaesthemes’ conceptual organization around some meaningful morpho-phonological clusters derived from Proto Indo-European, always connected with analogical associations. It also reasons about the stability of the root itself, due to fundamental characteristics of human cognition and broader social contexts in which language is used. Besides diachrony, the psycholinguistic relevance of phonaesthemic clusters is synchronically highlighted both in productivity – especially within the Germanic branch, English above all – and in comprehension processes, because their faciliatory priming effect seems to guide the speaker towards a better experience of understanding and to ease the progressive and natural addition of patterned neologisms after an existing word, in order to make them compatible with the original sets. The purpose of this contribution is to offer a general overview of the issue, trying, at the same time, to show how the phenomenon of phonaesthesia can also be read in the interaction between synchrony and diachrony, even if synchrony, for obvious reasons, remains the privileged investigation filter.