dossum

Colloquial form of dorsum. For the development of -rs- > -ss- compare prōsum, rūsum, sūsum (with subsequent shortening of -ss- after long vowels) and the Romance descendants of deorsum, ursus.

• (Proto-Romance) IPA^(key): /ˈdɔsso/

dossum n (genitive dossī); second declension

1. (Vulgar Latin) Alternative form of dorsum
   • [AD 98–138, Velius Longus, Henricus Keilius, editor, Liber de orthographia (Grammatici Latini; VII)‎, published 1880, lines 4–6, page 79:

     sic et dossum per duo s quam per r dorsum quidam ut lenius enuntiaverunt. ac tota r littera sublata est in eo quod est rusum et retrosum.

     And in this way, some [say] "dossum" with two s's instead of "dorsum" with an r to sound gentler. But to all, r is a sunk letter in "rusum" and "retrosum".]

Second-declension noun (neuter).