'appassionato' originates from Italian, specifically the word 'appassionato' (the past participle/adjective from the verb 'appassionare'), where the root 'passion-' relates to 'passion' or 'suffering' (from Latin).

'appassionato' developed in Italian from the verb 'appassionare' ('to inflame, to fill with passion'), which in turn derives from Late Latin 'passionare' and ultimately from Latin 'passio' ('suffering, passion'). It entered English usage mainly through musical terminology.

Initially it carried the general sense of 'made passionate' or 'filled with feeling'; over time its primary specialized use in English has become a musical direction meaning 'in a passionate manner' or 'with passion'.