Commentary Par XXVIII 105

The past definite tense of the verb terminare here is used in a dialectal form (as is vonno, with which it rhymes in [Par XXVIII 103]).  In De vulgari eloquentia (V.E.I.xiii.2), Dante had disparaged this (Pisan) dialectal form of the past definite ending (-onno), as commentators (beginning with Andreoli [DDP Andreoli.Par.XXVIII.104-105]) have taken pleasure in pointing out.  While both these words are forced by rhyme with (the apocopated form of possono) ponno, it seems evident that Dante enjoyed being forced into this 'ungrammatical' posture (i.e., presenting himself as employing a surprisingly low vernacular).  See C.Par.XVII.127-129.