Reconstruction talk:Proto-West Germanic/kokōn
The big question is whether such a verb really existed in PGmc, or whether the various putative reflexes in the daughters are actually independent derivatives. Points to consider:
1. As an *-ōną verb it is a denominative, created from a noun, conceivably *kukaz. Therefore we must look for the derivation of *kukaz from a Latin noun rather than a verb.
2. The Latin noun would seem to be Vulgar Latin cocus < Latin coquus (rather than the verb coquō~coquere)
3. The various daughter languages have cognate words for 'cook' (noun), given for example at <http://www.socialvocabulary.com/defines/cook.html>
4. Some indication of the time period(s) involved is given by Dennis Green, 'The Rise of Germania in the Light of Linguistic Evidence', in After Empire: Towards an Ethnology of Europe's Barbarians, edited by Giorgio Ausenda, Boydell & Brewer, 1995, pp. 143-162.
5. Green indicates that on the evidence of the vowel in 'cook' the word was borrowed (at least) twice into the Germanic languages, once to account for the short vowel of German Koch, the other to account for the long vowel of Old English cōc. Green's evidence is readily accessed on Google Books.
6. So, do we acknowledge a noun *kukaz < V.Lat. cocus in PGmc, with the verb *kukōną derived from the noun, or do we relegate the introduction(s) of the word to a later time period??
Let us consider for a moment the social and cultural circumstances of borrowing a culinary term from Latin, when there were existing terms for cooking, such as *brēdaną. At what time period would knowledge of cooking in Roman style have become salient enough in the backwoods of Germania Magna to warrant borrowing the term? Perhaps this is where the initial borrowing of the term as a noun rather than a verb is significant - it may have been circumstances in which the social role of cook was important. One such situation may have been the military. Perhaps Germani serving Rome became familiar with their military commander preferring his meals cooked by his own personal cocus/kukaz. This scenario would argue for a late rather than early borrowing.
Another dating tool may be the Latin Appendix Probi, written in the third or fourth century AD, which records the V.Latin form as a 'mistake': 'coquus non cocus'.
Dave Crowley