expono

Expono, exponere, exposui, expositum, third conjugation: ex plus pono, "put out". Note the perfect - pono's stem drops the n, so it is exposui and never exponui, and the participle is expositus.

Three lives run in parallel. Physically it is to set a thing out or unload a cargo on a shore. Brutally it is to expose an unwanted infant, the standard legal term for it, and half the foundlings of Roman comedy are expositi. In rhetoric and commentary it is to lay an argument out point by point, and that is the sense doing the work in this corpus, where a writer exponit a text verse by verse. English gets expound, exposition, exponent and exposure from the one verb.