'ascensiontide' originates from English, specifically the compound of 'ascension' and 'tide', where 'ascension' ultimately comes from Latin 'ascensio' meaning 'a rising' and 'tide' comes from Old English 'tid' meaning 'time' or 'season'.

'ascension' entered English via Old French from Latin 'ascendere'/'ascensio', and 'tide' comes from Old English 'tid'; the compound 'ascensiontide' appears in Middle English to denote the season or festival connected with the Ascension of Christ, eventually stabilizing into the modern English 'ascensiontide'.

Initially it meant 'the time/season of the Ascension', and over time it has remained largely the same, referring to either the liturgical period between Ascension Day and Pentecost or the festival/observance of the Ascension.