Etymology

Blackford means what it says, a black

Black

Black is the color of objects that do not emit or reflect light in any part of the visible spectrum; they absorb all such frequencies of light...

 ford or river-crossing. However, unlike other places of the name, it is a mix of Old English

Old English language

Old English or Anglo-Saxon is an early form of the English language that was spoken and written by the Anglo-Saxons and their descendants in parts of what are now England and southeastern Scotland between at least the mid-5th century and the mid-12th century...

 and Old Norse: the first element is Old English

Old English language

Old English or Anglo-Saxon is an early form of the English language that was spoken and written by the Anglo-Saxons and their descendants in parts of what are now England and southeastern Scotland between at least the mid-5th century and the mid-12th century...

blǣc "black

Black

Black is the color of objects that do not emit or reflect light in any part of the visible spectrum; they absorb all such frequencies of light...

", while the second element is Old Norse vathr / vaőr , ford, river crossing,
which usually occurs as -wath in place-names with this element (e.g. Wath upon Dearne). The name was recorded as Blakiwaith in 1165.