"morbid fear of being shut up in a confined space," coined 1879 (in article by Italian-born, French-naturalized Swiss-English physician Dr. Benjamin Ball), with -phobia "fear" + Latin claustrum "a bolt, a means of closing; a place shut in, confined place, frontier fortress" (in Medieval Latin "cloister"), from past participle of claudere "to close" (see close (v.)).
clausal
clause
claustral
claustration
claustrophilia
claustrophobia
claustrophobic
claves
clavichord
clavicle
clavier