More ill or unwell, or more disgusted or tired of something.
From Old English 'seoc' or 'sic' meaning 'ill,' related to Germanic roots. The comparative form adds '-er.' The slang meaning 'more amazing' is modern American English.
The phrase 'sick of it' used to literally mean something made you nauseous, but over time it shifted to mean 'tired of'—language often uses physical feelings to describe emotional states. Now young people have reversed it again, using 'sick' to mean 'cool,' showing how language cycles.
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