<unk>  was a term used for synthetic gases which emerged around 1670 when Robert Boyle coined the term upon isolating what is now understood to be hydrogen.<unk>  means "artificial, not natural", so the term means "man-made gases".
Factitious airs
Burning mouth syndrome
Oral allergy syndrome
Overbite
Cat bite
Snakebite
Dental abscess
Nasal fracture