Patronymic meaning son of Dennis, ultimately from Greek Dionysios, god of wine.
Dennison is an English patronymic surname meaning 'son of Dennis' or 'son of Denis,' with that root name descending from the Latin Dionysius — the Latinized form of Dionysus, the ancient Greek god of wine, ecstasy, theater, and fertility. The name traveled an extraordinary cultural distance from its origins: born in the vineyards and theatrical rites of ancient Greece, Dionysius was adopted by early Christians through Saint Denis, the third-century bishop of Paris who became France's patron saint and whose martyrdom — decapitated on a hill that would become Montmartre, reputedly carrying his own severed head to the site of his burial — made him one of the most dramatically venerated figures of medieval Christendom.
From Denis the saint, the name spread across medieval Europe, generating a cascade of diminutives (Dennis, Den, Denny) and patronymics (Dennison, Denison, Tennyson — the great Victorian poet Alfred Lord Tennyson bore the same etymological root). The surname Dennison appears in English records from the medieval period onward, carried by families across Britain and then throughout the English-speaking colonial world. As a given name rather than surname, Dennison occupies a distinguished, slightly formal register — fuller and more deliberate than Dennis, with the weight of its lineage made visible.
It suits those drawn to names that carry history without announcing it, names that reward a small amount of excavation. The journey from the grape-crowned god of ancient Athens to a name in a modern birth record is one of the longer and stranger arcs in Western naming history.