English
seroreaction
From sero- + reaction.
Proto-Indo-European *ser- ‘to flow, run’
Proto-Indo-European *sér-o- ‘flowing, liquid’
Proto-Italic *serom ‘liquid’
Latin serum ‘some other watery liquid’
English sero-
Proto-Indo-European *h₂eǵ- ‘to drive’
…
Latin reagō ‘to act upon again; to react’
Latin reāctiō ‘reaction’
Old French reaction
Middle English reaccion
English reaction
Today it means
noun reaction of blood serum (typically to a virus)
Language periods are conventional ranges, not dates for this word.
Etymograph / seroreaction