Figure of speech. While exchanging words with Joseph Patrick Nannetti over the unholy racket of the printing press, Bloom thinks, "He doesn't hear it. Nannan. Iron nerves." Nannan may be a nickname familiar to Dubliners, but in a chapter filled to bursting with rhetorical figures it also registers as a conscious manipulation of language. One possible label for it is antisthecon, the substitution of one letter, sound, or syllable for another within a word. Or a different kind of metaplasm, apocope, might apply.

John Hunt 2023

Two species of clown fish. Source: