Lukewarm

What is ‘luke’ warm?
 
The word ‘luke’ is from the 11th century Middle English term leuk (tepid), a word of uncertain origin, possibly from Middle Dutch leuk (tepid, weak) and Proto-Germanic khlewaz. This use of the word luke is now obsolete.
 
However, the word lukewarm (tepid; neither cold not hot) came to English in the late 14th century and has endured. In the 16th century, lukewarm also referred to a person lacking in zeal or enthusiasm.
 
I saw a cartoon recently: A clearly mild-mannered man sits at an office desk talking with a disappointed-looking person standing in front of him. “Sorry, I only deal with tepid button issues,” he says.
 
The Middle English term leuk is not to be confused with the Proto-Indo-European (PIE) root leuk (light, brightness) and Greek leukos (clear, white). These terms are the source of words such as elucidate, illustration, leukemia, lucid, luminate, luster, translucent, and many others.
 
Image: https://www.pinterest.ca/teambootcamp/gre-word-of-the-day/
 
Reference: Online Etymological Dictionary, https://www.etymonline.com/
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