Irregular long –o endings

English sometimes also uses the open o for spelling the long o-sound in word endings (‘no, go’ as opposed to ‘not, got’ where the  t  closes the vowel and makes it short).

The –o spelling has the alternative –ow (slow) and several others (50 –o v 59 others):
Go, no, fro, pro, so/sow/sew.
Ago, albino, also, armadillo, banjo, bingo, buffalo, cargo, cello, disco, domino, duo, dynamo, echo, Eskimo, flamingo, halo, hello, hero, judo, motto, piano, piccolo, Pluto, polo, potato, pseudo, radio, ratio, solo, soprano, studio, tango, tobacco, tomato, tornado, torpedo, trio, video, volcano, zero.
Blow, bow, crow, flow /floe, glow, grow, know, low, mow, row/ roe, show, slow/sloe, snow, stow, throw, tow/ toe.
Doe, foe, hoe, woe.
Dough, though.
Oh. Owe.
And in words of more than one syllable:
Arrow, barrow, bellow, below, billow, bungalow, burrow, elbow, fellow, follow, gallows, hollow, marrow, narrow, pillow, shadow, shallow, swallow, sorrow, sparrow, tomorrow, wallow, widow, willow, window, yellow.
Oboe. Cocoa. Pharaoh. Depot.

The pronunciation of –ough is famous for its variability: Though, through, cough, rough, bough (tho, throo, cof, ruf, bou). English words with -ough are all of Germanic origin, but in modern German their relations have phonic spellings (doch, durch, keuchen, rauh, Bug).

The –ow endings have two pronunciations and therefore create reading difficulties too (low now; follow allow), especially with the spellings of ‘bow, row’ and ‘sow’. These each spell two entirely different words, with different pronunciations in different contexts. The reading and spelling progress of young children would be greatly assisted by cutting the redundant letters after –o in all words which end with a long o-sound.

The different meanings and pronunciations of ‘bow, row’ and ‘sow’ (a red bou, bo your head; a loud rou, 1st ro, ro a boat; a fat sou, so some grass) show, once again, that spelling differentiations like 'flow /floe, row/ roe, so/sow/sew, slow/sloe, tow/toe' are completely gratuitous. Even if it was deemed that some of these must survive, the current memorisation burden for 109 words with –o/ -ow/ -oe/ -ough/ etc, could easily be made much smaller.

Early scribes and printers appear to have become muddled over the use of u and doubled u after o (thou, now, show). The doubled u after o in words which end with a long o-sound (blow, snow, show) is clearly redundant. It is another surviving relic from the common 16th practice of adding extra letters willy-nilly, like the many surplus –e endings discussed earlier.