From Proto-Italic *-kos, from Proto-Indo-European *-kos, *-ḱos. Cognate with Ancient Greek -κός (-kós), Proto-Germanic *-gaz, Sanskrit -शस (-śasa) and Proto-Slavic *-kъ.
PIE *-ko- on noun stems carried the meaning 'characteristic of, like, typical, pertaining to', and on adjectival stems it acted emphatically.
-cus (feminine -ca, neuter -cum); first/second-declension suffix
This suffix survives in inherited forms and became productive through its derivations (cf. infra) by metanalysis.
First/second-declension adjective.
| singular | plural | ||||||
|---|---|---|---|---|---|---|---|
| masculine | feminine | neuter | masculine | feminine | neuter | ||
| nominative | -cus | -ca | -cum | -cī | -cae | -ca | |
| genitive | -cī | -cae | -cī | -cōrum | -cārum | -cōrum | |
| dative | -cō | -cae | -cō | -cīs | |||
| accusative | -cum | -cam | -cum | -cōs | -cās | -ca | |
| ablative | -cō | -cā | -cō | -cīs | |||
| vocative | -ce | -ca | -cum | -cī | -cae | -ca | |