An Etymological Dictionary of the German Language/Kiefer
Kiefer (1.), m., from the equiv. MidHG. kiver (m., n. ?), kivel, kivele, ‘jaw, jawbone,’ besides which there is a form from the stem of kauen, MidHG. kiuwel, m., and usually kiuwe, këwe, f., ‘jaw, jawbone.’ Yet ModHG. kiver, kivel, have, notwithstanding their rare occurrence, a remoter history in the past; with Goth. *kifru- is connected OIc. kjǫptr, kjaptr (Goth. *kiftus), ‘mouth (of beasts), jawbone,’ and also with the a stage of gradation, AS. ceafl, OSax. kafl, m., ‘jaw of animals’ (with regard to the gradation comp. Käfer, Giebel, and Kerl). The Teut. stem is therefore kef, kaf, or rather keb, kab (before l and r later permutations of b to f sometimes occur), from pre-Teut. geph or gebh; comp. Zend zafare, zafra, n., ‘mouth, jaws’ (the corresponding term in Sans. *japhra, *jabhra, is wanting); the nasalised root jambh, by gradation jabh, ‘to snap at,’ leads to Gr. γαμφαΐ, γαμφηλαί, ‘jaws,’ yet these are probably connected more closely with the cognates discussed under Kamm. See Käfer.
Kiefer (2.), f., ‘pine,’ early ModHG. only; it cannot be traced further back; in UpG. Föhre simply. Hence Kiefer probably originated in Kienföhre (respecting the obscuration of old compounds comp. Wimper, Schultz, and Schuster). The intermediate form kimfer is recorded as North Boh. Comp. also MidHG. kienboum, m., ‘pine,’ and *kienforhe, f., ‘pine-tree’ (attested by the derivative kienforhîn, adj., ‘of pine’). Comp. Kien and Föhre.