'babysit' originates from English, formed by combining the noun 'baby' and the verb 'sit' (in the sense of 'sit with' or 'look after').

'baby' is from the English word 'baby' (a child) and 'sit' comes from Old English 'sittan'; the compound 'babysit' arose in modern English (chiefly 20th century) as a verb meaning to 'sit with a baby or child'.

Initially it literally meant 'to sit with a baby'; over time it became the standard verb for 'look after a child temporarily while parents are away' and also a noun for the job or occasion.