More unkind, cruel, or unpleasant in behavior or character; or more humble and of lower value.
From Old English 'mænan' meaning to lament or complain. The sense of 'unkind' developed from the idea of being small-spirited or petty. Also relates to 'mean' as in average or middle.
Meaner is confusing because it has two meanings—'more cruel' and 'more average'—and they come from completely different roots! Math uses 'mean' for average because it's the middle value.
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