Origin of solemn
SYNONYMS FOR solemn
In English, the extension of solemn from applying to rites, ceremonies, holy days, or oaths to nonreligious actions or feelings arose in the mid-15th century. One imagines early religious rites and ceremonies as being (like modern ones) serious and reverential affairs, and that the individuals performing or participating in them did so with a corresponding grave and serious demeanor. So it is not hard to see how the current sense of "grave, sober, or mirthless" developed: applying first to the people who participated in religious rites, and then losing the connection with the rites themselves.
Examples from the Web for solemnly
In America: The National Catholic Review, for example, John Nassivera solemnly intones that ectogenesis is “a very serious thing.”
These are not folks coming to solemnly worship during the several visiting hours open to non-Muslims.
Irene Prusik died that same month, and Parkin solemnly posed for a snapshot beside the open casket.Brooklyn’s Real-Life Norman Bates Accused of Cross-Dressing Fraud|Michael Daly|April 29, 2012|DAILY BEAST
“There is a revolution coming,” Professor Reich solemnly proclaimed.Could Mitt Romney Be the Last Baby Boomer to Run for President?|Michael Medved|April 25, 2012|DAILY BEAST
“So sad,” the former president of Pakistan muttered under his breath as he solemnly read the news from home.
I solemnly believe that we are facing another crisis in our history; it is slowly, gradually, inevitably and surely approaching.The Modern Ku Klux Klan|Henry Peck Fry
And most solemnly do I swear, that Miss Howe shall come in for her snack.Clarissa, Volume 4 (of 9)|Samuel Richardson
And then the waving banners, roaring cannon, and the slow procession, moving all too solemnly for our impatient wishes!Western Characters|J. L. McConnel
In the last writing of Thompson, he solemnly affirmed his belief in a "just and merciful God."The Story of a Strange Career|Anonymous
Then solemnly: Because the rattlesnakes dont kill em, an no one knows wherefore.The Sunset Trail|Alfred Henry Lewis