"renovate inner-city housing to middle-class standards," by 1972, from gentry + -fy. Related: Gentrified, which was used from early 19c. of persons.
Entries linking to gentrify
gentry n.
c. 1300, "nobility of rank or birth;" mid-14c., "a fashion or custom of the nobility;" late 14c., "nobility of character," from Old French genterie, genterise, variant of gentelise "noble birth, aristocracy; courage, honor; kindness, gentleness," from gentil "high-born, noble, of good family" (see gentle). Meaning "noble persons, the of well-born and well-bred people" is from 1520s in English, later often in England referring to the upper middle class, persons of means and leisure but below the nobility. Earlier in both senses was gentrice (c. 1200 as "nobility of character," late 14c. as "noble persons"), and gentry in early use also might have been regarded as a singular of that. In Anglo-Irish, gentry was a name for "the fairies" (1880), and gentle could mean "enchanted" (1823).
-fy
word-forming element meaning "make, make into," from French -fier, from Latin -ficare, combining form of facere "to make" (from PIE root *dhe- "to set, put").