Post History

**Note:** I am not an expert on Latin and I do not understand Latin. This answer is written purely from online research.

Using [Latin dictionary](http://www.latin-dictionary.net/list/letter/a) (39k+ Latin words) and leafing through each of the word pages and checking for matches with explicitly written Ks (regular expression `.+k.+ (adj|n|v|adv)`):

- A has 0
- B has 2
  - bekah, undeclined n
  - bikinianus, bikiniana, bikinianum adj
- C has 0
- D has 2
  - dikerion, dikerii n
  - dikerium, dikerii n
- E has 4
  - epimanikon, epimaniki n
  - epinikion, epinikii n
  - eukaristia, eukaristiae n
  - ektheta, ekthetae n
- F, G, H, I, J have 0
- K has 23
  - K., abb. n
  - kadamitas, kadamitatis n
  - Kaeso, Kaesonis n
  - Kal., abb. n
  - kalator, kalatoris n
  - kalatorius, kalatoria, kalatorium adj
  - Kalenda, Kalendae n
  - kalendarium, kalendari(i) n
  - kalo, kalare, kalavi, kalatus v
  - kalumnia, kalumniae n
  - kalumniator, kalumniatoris n
  - kalumniatrix, kalumniatricis n
  - kapitularium, kapitularii n
  - kaput, kapitis n
  - kardo, kardinis n
  - Karthago, Karthaginis n
  - karus, kara adj
  - katafractarius, katafractaria, katafractarium adj
  - katafractarius, katafractarii n
  - Kl., abb. n
  - koppa, undeclined n
  - kum, undeclined v
  - Kyrie, undeclined n
- L to R have 0
- S has 1
  - sokemannus, sokemanni n
- T to Z have 0.

This totals to 32 words, where the usage frequencies in text generally trend toward single digit number of mentions across a wider range of usage demographics and time periods, possibly implying its persistence. *bekah* is interesting here because it is used to denote half a *shekel* of currency, which is another word with letter 'k' in it. The use of *shekel* itself ranges from periods through 2150-300 BC, which means the letter remains relevant with the currency. Further analysis of names in times of high Latin usage may yield some insightful results.

Another part of the question says:

> one might expect K to be dropped in favor of C, yet it wasn't. What factors kept it alive in the language?

From Wikipedia's article on C<sup>[1]</sup>:

> In the Etruscan language, plosive consonants had no contrastive voicing, so the Greek 'Γ' (Gamma) was adopted into the Etruscan alphabet to represent /k/. Already in the Western Greek alphabet, Gamma first took a 'Early Etruscan C.gif' form in Early Etruscan, then 'Classical Etruscan C.gif' in Classical Etruscan. In Latin it eventually took the 'c' form in Classical Latin. In the earliest Latin inscriptions, the letters 'c k q' were used to represent the sounds /k/ and /ɡ/ (which were not differentiated in writing). Of these, 'q' was used to represent /k/ or /ɡ/ before a rounded vowel, 'k' before 'a', and 'c' elsewhere.[3] During the 3rd century BC, a modified character was introduced for /ɡ/, and 'c' itself was retained for /k/. The use of 'c' (and its variant 'g') replaced most usages of 'k' and 'q'. Hence, in the classical period and after, 'g' was treated as the equivalent of Greek gamma, and 'c' as the equivalent of kappa; this shows in the romanization of Greek words, as in 'ΚΑΔΜΟΣ', 'ΚΥΡΟΣ', and 'ΦΩΚΙΣ' came into Latin as 'cadmvs', 'cyrvs' and 'phocis', respectively.

'C' would have a replacement for more common sounds of 'K' (like before any vowel), but 'K' still remains in more special cases like *kalendae*<sup>[2]</sup> which refer to dates, and hence remain in daily use.

The Wikipedia article mentions the Greek Kappa, and often there is exchange and addition of words between similar languages, so some greek words have been assimilated into Latin. From etymonline's entry on K<sup>[3]</sup>:

> Little used in classical Latin, which at an early age conformed most of its words (the exceptions had ritual importance) to a spelling using -c- (a character derived from Greek gamma). In Late Latin, pronunciation of -c- shifted (in the direction of "s"). Greek names brought into Latin also were regularized with a -c- spelling, and then underwent the Late Latin sound-shift; hence the modern pronunciation of Cyrus, Circe. To keep their pronunciation clear, the many Greek words (often Church words) that entered Latin after this shift tended to take Latin -k- for Greek kappa.

The resurgence of K in Old English and French is also mentioned in the entry, but it mentioned to be *after* the rejection of K as redundant, so I think the this may be the probable reason for the retention of K in Latin.


[1]: https://en.wikipedia.org/wiki/C
[2]: https://www.thoughtco.com/latin-alphabet-changes-119429
[3]: https://www.etymonline.com/word/K#etymonline_v_1757