Mid 19th century; earliest use found in The Lancet. Alteration of either prodrome or prodromus, perhaps after words in -oma (although the semantic connection is not exact), or perhaps as a supposed Latin equivalent to ancient Greek προδρομή an instance of running forward (although this would not explain either of the plural forms), or perhaps originally a plural in form prodroma after ancient Greek πρόδρομα, neuter plural of πρόδρομος.