'altissimo' originates from Italian, specifically the word 'altissimo', where 'alto' meant 'high' and '-issimo' is a superlative suffix meaning 'very' or 'most'.

'altissimo' was borrowed directly from Italian into English, maintaining its original form and meaning.

Initially, it meant 'very high' in a general sense, but over time it evolved into its current specific musical context of 'highest register'.