'blur' originates from English, probably influenced by dialectal or imitative sources (compare Scots 'blurr'), where the root conveyed the idea of 'becoming or making dim or smeared'.

'blur' appears in English in the late 16th to early 17th century (from dialectal forms such as 'blurr') and developed into standard English 'blur'; the adjective 'blurred' and adverbial form 'blurredly' followed by affixation ('-ed', '-ly').

Initially it carried the sense of 'to smear or make dim'; over time it came to mean more broadly 'to make or become indistinct or unclear' and is now used for both visual and figurative lack of clarity.