Jakdan's Wordplay

I've been thinking about how Jakdan translated 自去自來 in Du Fu's poem. He could have translated it literally, cihai genere cihai jiderengge, but instead he wrote cihai deyenere cihai donjirengge.

What has he done here, and why?

Most obviously, Jakdan has told us that the swallows are flying (deyene-). Du Fu, in his elegant concision, did not say that they were flying. But then he didn't need to, because everyone knows that swallows fly. Indeed, the constraints of regulated verse may have made it difficult or impossible Du Fu to say "freely flying to and fro" (*自飛去來).

Jakdan, however, was not working under the same constraints as Du Fu. He imposed on himself the restriction that each line of his translation should have seven Manchu words, but was able to make use of the fact that Manchu can combine the meaning of "flying" (deye-) and "going" (-ne-) into a single word to embellish the translation without breaking the poetic form.

Perhaps more interesting, though less obvious, is what at first appears to be a transcription error in the word donjirengge. Just as Manchu can inject the meaning of "going" using the derivational suffix -ne-, it can likewise inject the meaning of "coming" using -nji-. If Jakdan meant to parallel Du Fu's 自去自來, we would expect cihai deyenere cihai deyenjirengge. However, instead of "come flying" (deyenji-), Jakdan gave us "listen, hear" (donji-).

The simplest explanation here is that Jakdan (or a copyist) made a mistake, and this is really meant to be deyenjirengge. However, I am entertaining the idea that Jakdan intended to embellish his translation again by telling us that people can hear the swallows, and he was poetically licensed to do this by the similarity between the words deyenji- and donji-.