Latin adverbs ending in -us

Question

There is a small but noticeable subset of Latin positive adverbs that end in -us. (By "positive," I am excluding the standard comparative adverb form of -ius, e.g. citius.)

Some examples that come immediately to mind are penitus, protinus, caelitus, divinitus, and (my favorite) medullitus. I also appended a list of such adverbs at the bottom of this question, though some (like adversus) are simply taken from the corresponding adjective.

Can anyone elucidate why these adverbs formed in this way?

Complete list:

adversus, advorsus, aliorsus, aliovorsus, aliquatenus, alterinsecus, alterius, alterorsus, altrimsecus, altrinsecus, antiquitus, caelitus, circumsecus, claritus, coelitus, cominus, comminus, communitus, conmunitus, controversus, cordetenus, cordicitus, corsus, deintus, demus, demus, deorsus, deversus, dextrorsus, dextroversus, dextrovorsus, dius, divinitus, eatenus, eminus, exadversus, exterius, extrinsecus, forinsecus, funditus, fundius, hactenus, humanitus, interdius, intrinsecus, introrsus, introsus, intus, laevorsus, medullitus, mordicus, nihilominus, nominetenus, nudius, nudiustertius, nullatenus, penitus, peropus, perpensius, potius, primitus, prius, prorsus, prosus, protinus, publicitus, quadamtenus, quadantenus, quamtocius, quamtotius, quandius, quantocius, quatenus, quatinus, quoquoversus, quorsus, radicitus, retrorsus, retroversus, rursus, secius, secus, seorsus, sequius, seriosius, serius, setius, sinisbrorsus, sinisbrosus, sinistrorsus, solemnitus, sollemnitus, subtus, superficietenus, terratenus, ullatenus, undiquesecus, undiquesecus, utrimquesecus, versus, vorsus,

Answer 1

Lewis & Short say -tus in intus is an old ablative ending or suffix, related to the Greek adverbial ending -τός as in ἐντός:

intus, adv. [1. in and the abl. termination -tus; Sanscr. -tas; cf. ἐντός].

Most of the words on -tus in your list seem to contain the same suffix.

A suffix -tus often turns into -sus, as in ordinary past participles like passus, versus, missus, mansus, caesus. This may explain many of the adverbs in -sus.

I wonder whether this ablative could be related to the ablative plural ending -bus.

dēmum (also demus, like prorsus, quorsus, rursus, deorsus...), adv. [a sup. form from de, downmost; cf.: sub, summus]

The entry for demus in L&S says simply "see demum". So it seems likely that both demus and demum are superlative forms ("sup." stands for superlative here, not supine).

Apparently, both an -us form and an -um form of a superlative could be used to express something adverbial. So the ablative suffix -tus in intus need not be derived from the supine stem on -tu-, since superlatives are standard consonantal stems without a u in the stem—unless superlatives could also have -u- in archaic/proto-Latin.

Many of the words are derived from versus/vorsus, like prorsus, quorsus, rursus, deorsus, introsus, seorsus.

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L&S say tenus is different, perhaps being originally an accusative of direction. It makes sense that it should be different, since it functions as a postposition in classical Latin, not an adverb. Only with a prefixed ablative does it become an adverb (hac tenus).

tĕnus [root ten; v. teneo], perh. orig., an acc. of direction, and hence joined with gen.; afterwards a prep. with abl.

Neither L&S nor De Vaan explain the ending of adverbial secus, except in so far that it was originally an adjective or participle probably derived from the same root as sequor.

Many of the words in your list are accusative neuter forms of comparatives, with the ordinary neuter comparative suffix -(i)us, genitive -(i)oris. Among those I would group almost all of the words on -ius, and minus.

Peropus must be per opus, where opus is simply the neuter noun opus, in the accusative singular as dictated by the perposition per.