Named from Jocelyn Cottage" and grounds, situated on the leading road to Cregagh. It was a neat cottage, with some 20 acres of a land, gardens, plantations, and a porter's lodge". (Belfast Street Names. John J. Marshall).
Jocelyn is a male forename of Frankish origin which entered English via Norman French. It became a female name through revival in the 20th century. However, it can also be a surname and it may be significant that it was the family name of the Earls of Roden.
"On the recommendation of the city surveyor, the committee approved of the street name Jocelyn Gardens being given to a new throughfare in continuation of Jocelyn Gardens for Miss H. E. Megarry". (22nd May 1956).