We report on a subplinian eruption fed by a picritic magma that occurred 3930 ¿ 60 BP at Etna volcano. The eruption produced a fallout deposit of 0.183 km3 (0.055 km3 DRE), widely dispersed eastward, which represents a marker bed for the Holocene stratigraphy of the volcano. Tephra have a composition of nearly primary magma, owing to their high Mg# (72--79). Glass geothermometry indicates eruptive temperatures (1159--1171¿C) ≈ 100¿ higher than those measured in recent eruptions. High volatile content and unusual enrichment of LIL elements in feeding magma, both suggest addition of fluids in the source zone accounting for a large production of highly buoyant fast-rising melt. Vigorous degassing of volatile-rich picritic magma is responsible for the explosive nature of this eruption.