A single bubble formed in soapy water. Often used in plural form 'suds' to refer to foam or lather produced by soap or detergent in water.
Possibly from Middle Dutch sudde meaning 'marsh, bog' or related to Old English sēoþan 'to boil, seethe.' The connection may be through the bubbling action of boiling water resembling soap foam. First recorded in English in the 16th century.
While we usually encounter 'suds' in the plural, the singular 'sud' reveals the individual poetry of each soap bubble. The word's possible connection to marshes and bogs suggests our ancestors saw similarity between natural foam in wetlands and the artificial foam of soap-making.
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