A folder with rings or clips for holding loose papers together, or any device that binds things.
From Old English 'bindan' meaning 'to tie' or 'to make fast,' related to 'bind.' But the surprising connection is to Sanskrit 'bandh' meaning 'to bind,' which also gave us 'band,' 'bond,' and even 'husband' (literally 'house-binder' or one who binds the household together). Ancient Indo-European speakers were obsessed with tying things together!
Your school binder shares DNA with the word 'husband' - both come from ancient words about binding and tying things together! Indo-European cultures were so focused on binding and securing that this root spread into dozens of modern words about connection and commitment.
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