Generally regarded as deriving from rotō (“turn, revolve”) or rota (“wheel”) + -undus. First attested in the works of Cato the Elder (circa 200 BC).
It has also been suggested that the alternative form retundus, whence most of the Romance descendants derive, actually reflects the original Latin form (despite only being attested from the seventh century CE). If so, the first element would derive from an older *retō, from Proto-Indo-European *Hreth₂- (cf. Proto-Celtic *reteti), and the Classical rotundus would reflect later influence from rota (“wheel”).
rotundus (feminine rotunda, neuter rotundum, comparative rotundior, superlative rotundissimus); first/second-declension adjective
First/second-declension adjective.
| Number | Singular | Plural | |||||
|---|---|---|---|---|---|---|---|
| Case / Gender | Masculine | Feminine | Neuter | Masculine | Feminine | Neuter | |
| Nominative | rotundus | rotunda | rotundum | rotundī | rotundae | rotunda | |
| Genitive | rotundī | rotundae | rotundī | rotundōrum | rotundārum | rotundōrum | |
| Dative | rotundō | rotundō | rotundīs | ||||
| Accusative | rotundum | rotundam | rotundum | rotundōs | rotundās | rotunda | |
| Ablative | rotundō | rotundā | rotundō | rotundīs | |||
| Vocative | rotunde | rotunda | rotundum | rotundī | rotundae | rotunda | |
(See also retundus, *torundus.)