eyelet hole
/ˈʌɪlɪt ˌhəul/noun
1= eyelet.
2A hole or opening for looking through; a small window or window-like opening. Formerly also: an opening in a wall through which missiles may be discharged. Compare earlier oillet. Now rare.
Origin
Late 16th century. From eyelet + hole, perhaps as a remodelling of earlier oillet-hole.