The quality of being slow to understand, thick-headed, or lacking in intelligence or sensitivity.
From 'blockish' (block-like, stupid) plus '-ness' suffix meaning 'state of being.' Block has meant 'dull person' since the 1500s.
The word 'blockish' comes from comparing a dull person to a block of wood—one of those metaphors so apt that it stuck around for 500 years.
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