'aspergillum' originates from Medieval Latin, specifically the word 'aspergillum', a diminutive formed from Latin 'aspergere' meaning 'to sprinkle'.

'aspergere' (Latin, 'to sprinkle') gave rise to the diminutive Medieval Latin form 'aspergillum', which entered English via ecclesiastical/Latin usage in the Middle Ages as the term for a small sprinkler used in liturgy.

Initially it meant 'little sprinkler' (a diminutive of 'to sprinkle'); over time it became specialized to refer specifically to the liturgical instrument for sprinkling holy water.