inoculate: [15] Far-fetched as the connection may seem, inoculate actually comes ultimately from Latin oculus ‘eye’ (source of English ocular [16] and oculist [17]). By metaphorical extension oculus was applied to the ‘bud’ of a plant (much like the eye of a potato in English), and the verb inoculāre was coined to denote the grafting on of a bud or other plan part.
That was how it was used when originally adopted into English (‘Peaches have their Season at May Kalends them to inoculate’, Palladius on Husbandry 1440), and the modern sense ‘introduce antigens into the body’ did not emerge before the early 18th century, based on the notion of ‘engrafting’ or ‘implanting’ an immunising virus into a person. It was originally used with reference to smallpox. => eye, ferocious, ocular
