'ictus' originates from Latin, specifically the noun 'ictus', the past participle noun form related to the verb 'icere' (to strike), where the root conveyed the idea of a 'blow' or 'strike'.

'ictus' passed into English via Late Latin and Medieval Latin with the sense 'a blow' or 'stroke'; the word was adopted into English medical, musical, and poetic terminology largely in the 17th–19th centuries without major phonetic change.

Initially it meant 'a blow or strike' in Latin; over time the sense broadened in English to include 'a sudden medical attack (stroke)', and specialized technical senses in music and prosody meaning 'a beat' or 'stress'.