Wet, boggy, and filled with water and mud; resembling or containing swamps.
From 'swamp' (possibly from Algonquian languages encountered by English colonists) plus '-y' meaning 'full of' or 'resembling'; became common in 17th-century American English.
Early colonists in America learned the word 'swamp' from Native Americans, and it perfectly captures that specific type of watery wilderness—so when they added '-y' to make 'swampy,' they were describing a landscape that would shape American history and geography.
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