'Eastertide' originates from Old English elements: 'Easter' (from Old English 'ēastre' or 'ēostre') and 'tide' (Old English 'tīd'), where 'ēastre/ēostre' referred to the festival of spring (Easter) and 'tīd' meant 'time' or 'season'.

'Eastertide' developed in Middle English as a compound of 'Easter' + 'tide' (written as 'Eastre-tīd' / 'Ester-tide' in Middle English) and eventually became the modern English 'Eastertide'.

Initially, it simply denoted the 'time or season of Easter', and over time it has retained that central sense while being used both in formal liturgical contexts and in general/poetic reference to the Easter period.