^Kulla, Ariola (2010),The Albanian Linguistic Journey from Ancient Illyricum to EU: Lexical Borrowings[1], Linköping University, Department of Culture and Communication, page21
The Esperanto suffixes-as,-is,-os,-us are related, and appear to have been inspired by previous language projects:
This play of vowels is not an original idea of Zamenhof's:-as,-is,-os are found for the three tenses of the infinitive in Faiguet's system of 1765;-a,-i,-o without a consonant are used like Z's-as,-is,-os by Rudelle (1858); Courtonne in 1885 had-am,-im,-om in the same values, and the similarity with Esperanto is here even more perfect than in the other projects, as-um corresponds to Z's-us. —An International Language (1928)
The vowel of-as is likely cognate with the Latin present, as inamat(“s/he loves”), and the corresponding present infinitiveamāre, permitting the natural (for a European)-ant ending.i could come from past tense in Latinami,amisti.
Franz Boas, Helene Boas Yampolsky & Zellig S. Harris (1947), “Kwakiutl Grammar with a Glossary of the Suffixes”, inTransactions of the American Philosophical Society[3], volume37, number 3, page318
In an exception to the usual Latin stress rule, Latin words ending in this suffix were generally stressed on the final syllable of their nominative singular forms in-ās because of the aforementioned syncope.
FromProto-Italic*-ās, fromProto-Indo-European*-éh₂(e/o)s, the genitive singular of*-éh₂. Despite the existence of a few relic survivals in fixed expressions, this ending was largely displaced already in Old Latin by-āī (formed by analogy to the second-declension genitive singular ending-ī), which evolved to the Classical Latin genitive singular ending-ae.
Unclear. Possibly derived fromProto-Italic*-ās, fromProto-Indo-European*-éh₂es, the nominative/vocative plural of*-éh₂. Rather than being inherited, it has been speculated that this ending was borrowed from Oscan (another Italic language). Alternatively, possibly taken from the accusative ending.[1]
Perhaps from the Proto-Germanic accusative plural ending *-anz, with regularly lost-n- before a fricative, or perhaps from the nominative plural *-ōs, a voiceless variety of the regular ending *-ōz, or a merger of both. Akin toSaterland Frisian-s,West Frisian-s,Old Saxon-os (Low German-s),Dutch-s,Swedish-ar.
Inherited fromOld Galician-Portuguese-as, a merger ofLatin-ās (used with residual third conjugation non-i-stem verbs) withLatin-eās (used with Proto-Romance verbs in-ēre, which merged Latin second and third conjugation verbs) andLatin-iās (used with Proto-Romance verbs in-īre). Thee/i in hiatus would have disappeared after palatalizing the previous consonant, which survives in some irregular verbs but has largely been analogically eliminated. CompareGalician andSpanish-as.
FromLatin-eās,Latin-ās, andLatin-iās, the second-person singular present active subjunctive endings of second, third, and fourth conjugation verbs, respectively.
R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke et al., editors (1950–present), “-as”, inGeiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies