'corollary' originates from Latin, specifically the word 'corollarium', where 'corolla' meant 'a little garland' (diminutive of 'corona' meaning 'crown').

'corollary' changed from Late Latin 'corollarium' (originally meaning a small garland or a gratuity) into Medieval/Late Latin sense 'a thing given in return' and then into the logical sense 'a consequence', eventually entering Middle English as 'corollary' with the modern meaning.

Initially, it meant 'a small garland' or 'a gratuity'; over time it evolved into the sense of 'a consequence' or 'something that follows naturally', which is the primary modern meaning.