Diminutive

“Diminutive (noun): A word or word element indicating (often by addition of a suffix) small size or familiarly lovable, pitiable, or dismissible qualities, sometimes condescendingly. Adverb: diminutively.

‘My grandmother, too, used to put other people’s ailments into the diminutive; strokelets were what her friends had. Aldo said he was bored to tearsies by my grandmother’s diminutives.’ Renata Adler, Speedboat“

Excerpted from: Grambs, David. The Random House Dictionary for Writers and Readers. New York: Random House, 1990.