'pensively' originates from English, specifically the adjective 'pensive' with the suffix '-ly', where '-ly' meant 'in the manner of'.

'pensive' came into English via Middle English from Old French 'pensif', which itself derives from Latin 'pensare' (frequentative of 'pendere'), meaning 'to weigh, to consider'. The adverb 'pensively' was formed later in English by adding the adverbial suffix '-ly' to 'pensive'.

Initially related to the idea of 'weighing' or 'considering' (literal sense of assessing or weighing mentally), over time it evolved to mean 'thoughtful, often with sadness or wistfulness', which is the modern sense of 'pensively'.