swer-
“to swear, to speak solemnly”swear
PIE root meaning to swear or speak solemnly. Source of English "swear," Latin sermo, and words for formal oaths.
Discussion
*swer- is a Proto-Indo-European root meaning "to swear" or "to speak solemnly," yielding vocabulary for oaths, formal speech, and solemn declarations.
The root gives Old English swerian "to swear" (modern English swear), with the original meaning of making a formal, binding oath rather than using profanity. German schwören "to swear" and Dutch zweren continue the Germanic form. Old Norse sverja yields the same.
Latin sermō "speech, conversation" (whence English sermon) derives from a form *swer-mon-, with the semantic shift from solemn speech to speech generally. The connection between swearing oaths and sermons—both forms of weighty, consequential speaking—is preserved in this etymological link.
In Slavic, Old Church Slavonic svara "quarrel" shows a semantic extension from formal disputation to conflict. The root connects to PIE legal and social vocabulary, where oath-taking was central to justice, alliance, and governance.
The modern English split between swear (oath) and swear (profanity) developed in Middle English—the profane sense arose from the taboo against casual oath-taking. Modern descendants include English swear, answer ("to swear back"), and through Latin: sermon.
Notes
Source of English "swear", "answer" (swear back). Germanic *swarjan.