Farrow is a hypercorrected form of Ferror (Farrar), an occupational surname for a blacksmith or an ironworker, an old name of early Medieval English and French origin. The name derives from the Middle English and Old French terms "ferrer, ferreor, ferrur, ferour" (meaning "smith"), derivatives of "fer" (meaning "iron" in French), from the Latin "ferrum". The development of the surname shows the usual Medieval English change in pronunciation (and thence spelling) from "-er" to "-ar" and "-ow" endings.

Due to varying levels of literacy, and regional dialects the name morphs back and forth from Farrar, Pharo, Farra, Ferrar, Farrer, and Farrow, the name itself did not change, but the spelling of it depended upon the scrivener.

The surname is found, in England, originally in those areas in which there were deposits of iron and thus an iron producing industry.

Bearers of the surname belong to various haplogroups including E-M2, I-M233, I-M253,J-M172, R-M269, R-YP5578