AAPKA DICTIONARY NO FURTHER A MYSTERY

There isn't any nominal pairs for tense/lax pairs such as /ʊ/ and /u/ in unstressed syllables, given that they are in complementary distribution. They don't seem to be actually various phonemes."servus" (also typically pronounced "seavus") arrives most likely from Latin "servus", as some other people have already pointed out. What I'm not convince