Auditorium

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early 17th century (originally in the general sense ‘a place for hearing’): from Latin, neuter of auditorius ‘relating to hearing’ (see auditory).

wiktionary

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Borrowed from Latin audītōrium, from audītōrius(“pertaining to hearing”). Equivalent to auditory +‎ -ium.

etymonline

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auditorium (n.)

"part of a public building where people gather to hear speeches, etc.," 1727, from Latin auditorium "a lecture-room," literally "place where something is heard," in Medieval Latin especially "a reception room in a monastery," noun use of neuter of auditorius (adj.) "of or for hearing," from auditus, past participle of audire "to hear" (from PIE root *au- "to perceive"); also see -ory. Earlier in English in the same sense was auditory (late 14c.).