'scrofula-preventing' originates from Modern English as a compound of the noun 'scrofula' (from Latin 'scrofula') and the present participle 'preventing' of the verb 'prevent' (from Latin 'praevenire', where 'prae-' meant 'before' and 'venire' meant 'to come').

'scrofula' entered English from Latin 'scrofula' (used in medieval and early modern medical Latin for tuberculous swelling of the neck). 'Prevent' developed from Latin 'praevenire' → Old French 'prevenir' → Middle English forms (e.g. 'prevenen') and then Modern English 'prevent'; the present participle form gave 'preventing'. The modern compound simply joins the noun and participle into an adjectival phrase.

Initially the elements referred separately to the disease ('scrofula') and the action of stopping something ('prevent'); over time combining them created a transparent adjectival compound meaning 'able to prevent scrofula' with no major semantic shift beyond compositional meaning.