One of the mysteries of the English language finally explained.
Synonyms of common in English:
common
See definition of common
adjective
1‘he gained a massive following among the common folk’
ordinary, normal, typical, average, unexceptional, run-of-the-mill, plain, simple
2‘this booklet answers the most common questions asked’
usual, ordinary, customary, habitual, familiar, regular, frequent, repeated, recurrent, routine, everyday, daily, day-to-day, quotidian, standard, typical
conventional, stock, stereotyped, predictable, commonplace, mundane, run-of-the-mill
literary wonted
unusual
3‘it is a common belief that elephants have long memories’
widespread, general, universal, popular, mainstream, prevalent, prevailing, rife, established, well established, conventional, traditional, traditionalist, orthodox, accepted
in circulation, in force, in vogue
rare
4‘they work together for the common good’
collective, communal, community, public, popular, general
shared, joint, combined
private, individual
5‘the fishermen's wives were far too common for my mother’
uncouth, vulgar, coarse, rough, unsavoury, boorish, rude, impolite, ill-mannered, unladylike, ungentlemanly, ill-bred, uncivilized, unsophisticated, unrefined, philistine, primitive, savage, brutish, oafish, gross
lowly, low, low-born, low-ranking, low-class, inferior, humble, ignoble, proletarian, plebeian
informal plebby, slobbish, cloddish, clodhopping
British informal common as muck
archaic baseborn
refined, noble