Roby
Usually a surname from Robert, though in northern England it can also be locational, from a Lancashire place-name.
The #3,798 most common surname in the United States (2010 Census) — about 1 in every 33,145 Americans shares it.
Etymology
Most surname references treat Roby as a short form or spelling variant connected with Robert, ultimately from the Germanic name meaning roughly 'bright fame.' In northern England, however, some sources also connect it with the Lancashire place-name Roby, which was recorded in medieval forms such as Rabi, Robi, and Robye. That place-name is commonly explained from Old Norse elements, either referring to a 'roe' place or to a settlement in a nook or corner.
History
The name appears in English records in several spellings, and later dictionaries often link it to the widespread Robert-name group, including Robson, Robbins, and Robson-type forms. At the same time, the Lancashire place-name Roby clearly existed early and may have contributed to surname use in that region. Because both explanations appear in the older scholarship, modern treatments usually keep the origin a little open rather than forcing a single derivation.
Origin
Regions
Variant spellings
Fun fact
Older surname dictionaries disagree here: one treats Roby as a Robert-name form, while another also points to the Lancashire place-name Roby as a possible source.
From the historical record
“ROBSON, Rob's Son : v. Rob. ROBY (Scand.) Bel. to Roby = i RA's or the Roe Stead [O.N. rd, a roe + hy-r\ 2 the Farm in the Nook or Corner [O.N. ti)rd, a nook, corner -t- by-r] The Lancashire Roby was Rabi in the 1 2th and 13th cent; Robi and Roby{e in”
— Surnames of the United Kingdom: a concise etymological dictionary (2 vols in 1)