The Ancient Greek datives in ‐essi have posed a longstanding challenge in Greek linguistics, with their traditional categorisation as ‘Aeolic’ but their widespread presence across Aeolic and non‐Aeolic regions. This article investigates the origin and diffusion of this trait, examining both the early Greek evidence (in particular the Lesbian poets, Homer, and Mycenaean Greek) and that from specific areas, namely Sicily and Pamphylia, which are often overlooked despite their history of language contact. We argue that it is not necessary to have a single explanation for the origin and spread of ‐essi and that independent innovations in Greek dialects better account for the material. Despite the lack of a unitary account, we suggest that something comparable to the concept of “drift” could underlie such a development. By analysing the epigraphic evidence from Sicily and Pamphylia, we conclude that the presence of ‐essi cannot be solely attributed to contact in all the areas in which it is attested. This perspective challenges the notion of ‐essi as a strong dialectal isogloss useful for diachronic dialectal taxonomy. More generally, this case study confirms the importance of considering diachronic typology and language contact to gain a more comprehensive understanding of language change.