claustellum

• clostellum

From claustrum (“bar, gate”) +‎ -lus.

• (Classical Latin) IPA^(key): [kɫau̯sˈtɛl.lũː]
• (modern Italianate Ecclesiastical) IPA^(key): [klau̯sˈt̪ɛl.lum]

claustellum n (genitive claustellī); second declension

1. keyhole
   • c. 27 CE – 66 CE, Petronius, Satyricon 140:

     Itaque ego quoque, ne desidia consuetudinem perderem, dum frater sororis suae automata per clostellum miratur, accessi temptaturus an pateretur iniuriam.

     Therefore, fearing through inaction I might lose an opportunity, I also made advances to the brother who was enjoying the gymnastics of his sister through the keyhole, to see if he would prove amenable to assault.

Second-declension noun (neuter).

• (keyhole): forāmen

• Italian: chiavistello