Dreamer

wiktionary

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From Middle English dremer, dremere, dremare, equivalent to dream +‎ -er. Cognate with West Frisian dreamer(“dreamer”), Saterland Frisian Dröömer(“dreamer”), Dutch dromer(“dreamer”), German Träumer(“dreamer”), Danish drømmer(“dreamer”), Swedish drömmare(“dreamer”).

etymonline

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dreamer (n.)

early 14c., "one who dreams," agent noun from dream (v.). Meaning "idler, daydreamer" emerged by late 14c. Old English dreamere meant "musician."