1. Mildly warm; tepid.
2. Lacking conviction or enthusiasm; indifferent: gave only lukewarm support to the incumbent candidate.
[Middle English leukwarm : leuk, luke (possibly alteration of leu, from Old English hlēow; see kelə-1 in the Appendix of Indo-European roots) + warm, warm; see WARM.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.