When the Krill are about to board their vessel, they say a prayer for the crew of the Orville in their native language. As the Orville crew are all equipped with translators (as that is presumably how they have been communicating with the Krill, who would not lower themselves the speak in the language of lesser beings), there would seem to be no reason that bit of dialogue should have been untranslated while the rest of their speech was heard in English.
However, many cultures have a religious or poetic language (usually archaic) which is distinct from their ordinary day-to-day speech. It may be that this prayer is in one such specialized Krill language, and thus unknown to the translators.
