Why is sew (
/sō/) pronounced similar to so rather than to few or sue?
Looking at its etymology,
Old English siwian "to stitch," earlier siowian, from Proto-Germanic *siwjanan (cf. Old Norse syja, Swedish sy, Old High German siuwan, Gothic siujan "to sew"), from PIE root *syu- "to bind, sew" (cf. Sanskrit sivyati "sews," sutram "thread, string;" Greek hymen "thin skin, membrane," hymnos "song;" Latin suere "to sew, sew together;" Old Church Slavonic sijo "to sew," sivu "seam;" Lettish siuviu, siuti "to sew," siuvikis "tailor;" Russian svec "tailor"). Related: Sewed; sewing. Sewing machine is attested from 1847.
siowian appears to be the only word which could have been pronounced with a
/səʊ/. But the later spelling of siwian sounds unlikely to have been pronounced so.
Also, are there other similarly spelt words which have the same irregularity in pronunciation?