'lectionary' originates from Medieval Latin, specifically the word 'lectionarium', where 'lectio' meant 'reading' and the root 'legere' meant 'to read'.

'lectionary' changed from the Medieval Latin word 'lectionarium' into Middle English 'lectionarie' and eventually became the modern English word 'lectionary'.

Initially, it meant 'a book containing readings,' but over time it also came to mean 'the system or schedule of appointed readings used in liturgy'.