solemn vs unobserved

solemn

adj
  • Characterized by or performed with appropriate or great ceremony or formality. 

  • Of or pertaining to religious ceremonies and rites; (generally) religious in nature; sacred. 

  • Inspiring serious feelings or thoughts; sombrely impressive. 

  • Deeply serious and sombre; grave. 

unobserved

adv
  • whilst not being seen or observed 

adj
  • Not seen or observed. 

How often have the words solemn and unobserved occurred in a corpus of books? (source: Google Ngram Viewer )