From kata and heko; to reach to, i.e. (neuter of present active participle, figuratively as adjective) becoming -- convenient, fit.
see GREEK kata
see GREEK heko
1. to come down.
2. to come to, reach to; impersonally, καθήκει, it is becoming, it is fit (cf. German zukommen), Ezekiel 21:27; οὐ καθῆκεν (Rev. καθῆκον), followed by the accusative with an infinitive, Acts 22:22 (Winers Grammar, 282 (265); Buttmann, 217 (187)); τά μή καθήκοντα, things not fitting, i. e. forbidden, shameful, Romans 1:28; 2 Macc. 6:4. Cf. ἀνήκω.