Korowai of West Papua practice a register of transgressive vocabulary substitutions in which a referent's normal designation is replaced by another expression with independent semantic meaning. Uttering a substitute term in the presence of its referent is thought to damage the referent. Usually the terms are carefully avoided, but they can also be deliberately uttered in anger. Substitutions highlight uncanny iconic resemblances between entities that are otherwise mutually incongruous. Substitutions often involve grotesque imagery of bodily disintegration, and they focus on strange margins close to humans' positions. Speakers use the register to portray uncertainty about the categorial integrity not just of referents but also of language users themselves. Through the register's core idea of avoiding damaging effects of iconic connections beneath fragile surface appearances, Korowai express a reflexive sensibility about language, in which transparently affirmative semantic relations between words and referents are a contingent pragmatic possibility, not a natural certainty.