It ' s completely valid for phonology to refer to lexical information . Since the words which would support a phonemic interpretation of are a extremely limited in number , and b exclusively of nonnative origin or onomatopoeic in nature , it is not unreasonable to posit that they are lexically specified for as members of very specific lexical classes . The data is overwhelmingly in favour of an interpretation of and as being in complementary distribution . The conditioning for this allophony is entirely natural easily defined in terms of phonological features . The offending wordinitial position can hence be considered to be underspecified for frontnesscentralness . wordonset i is underspecified , surface realisation free to a certain extent i receives specification from velarised onset consonant and surfaces as , entirely predictable underlyingly ib but lexically specified for The argument from etymology is in fact more persuasive than you give it credit for even if you can overlook the complementary distribution and postulate a phoneme , you are bound to notice that it never occurs in closedclass words , nor in any words of native provenance which are not onomatopoeic , and it does not underlie full minimal pairs as far as I know . This suggests that , if it is a phoneme , it is one of periphery rather than centre as far as the phonology is concerned . In this sense , it is common that nominal , contentoriented loans are peripheral and may require parsing tools which are alien to the language ' s own phonology Germans often pronounce Balkon with a nasal vowel seemingly distinctively so even though nasal vowels do not feature in the phonemic inventory of German . The same goes for onomatopoeia many languages have lexically specified onomatopoeia with surface phones which do not seem to be available from the language ' s phonemic inventory such as clicks for onomatopoeic words for disapproval or bilabial fricatives or trills for the whinnying of a horse in English .