'bahadur' originates from Mongolic/Turkic languages via Persian and South Asian usage, specifically from Middle Mongolian 'bagatur' or 'baatar', where that root meant 'hero' or 'brave'.

'bagatur' (Middle Mongolian) passed into various Turkic and Persian languages as forms like 'bahadur', then entered South Asian languages (e.g. Hindi, Urdu) as 'bahadur' and was later borrowed into English texts as a loanword meaning a brave person or honorific title.

Initially it meant 'hero' or 'valiant warrior'; over time it became used both as an honorific/title and as a surname, and in English contexts it refers to the title/surname or to brave persons generally.