English has a large stock of non-native vocabulary (i. e., words not of Germanic or Anglo-Norman provenience) whose pronunciation may still reflect their foreign origin. Typically, once such a word passes into common use, its pronunciation adjusts itself correspondingly to conform to traditional phonetic norms. At any intermediate stage between initial entry into English vocabulary and complete demoticization, there is usually some fluctuation involving doublets (two competing variants) before a historical resolution toward one as normative.
This process can be observed with two words that are currently in the news, synod (< late Latin synodus,< Greek σύνοδος assembly, meeting, astronomical conjunction, < σύν syn- prefix + ὁδός way, travel; reinforced later by French synode (16th cent.) and ebola (< Ebola, the name of a river and district in northwestern Zaire, where an outbreak of haemorrhagic fever occurred in 1976). The Oxford English Dictionary Online gives the following variant pronunciations for ebola: Brit. /iːˈbəʊlə/, /ᵻˈbəʊlə/, /ɛˈbəʊlə/, U.S. /ɪˈboʊlə/; but for synod all dictionaries register only one, namely /ˈsɪnəd/, despite the fact that one constantly hears the unstressed syllable pronounced with the full vowel of odd rather than the schwa alongside the normative pronunciation with the schwa.
In both words the American English pronunciation of something other than a reduced vowel ([ə] in synod and [ɪ] in ebola) in the unstressed syllable should be interpreted as a sign of its evaluation as a word of foreign origin. The value, specifically the markedness value, of the sounds at issue is what is at stake here. The appearance of a full vowel in unstressed position in dissyllabic words in English is marked, whereas that of a reduced vowel is unmarked. This follows from the value of reduced vowels as unmarked vis-à-vis their full vocalic counterparts. One way that demoticization of foreign words proceeds is by the gradual replacement of the marked vowel by the unmarked.
When persons who have either never heard the normative pronunciation of a word like synod or do not have it in their vocabulary start using it, the first result is to mark it as foreign by utilizing a full vowel (what might be called the “spelling pronunciation,” although the correct designation should be “reading pronunciation”) rather than the correct reduced vowel. In the speech of such persons the ultimate trajectory, when they have been exposed to sufficient instances of its use, is demoticization in the form of vowel reduction. The same is predictably true of ebola, as can already be heard in the pronunciation of some speakers of American English today.