late 14c., retentif, "able to hold or keep" (food, nourishment), from Old French retentif, from Medieval Latin retentivus, from past-participle stem of Latin retinere "to hold back, retain" (see retain).
The mental sense of "good at remembering, having a good memory" is from early 15c. The general sense of "having the property of retaining or keeping" is from 1580s. Related: Retentively; retentiveness.
updated on July 26, 2021