setjast í helgan stein

In old Icelandic the meaning of this idiom was "to join a monastery". In older times the adjective helgur ("holy") wasn't in the idiom however, and it was simply used in the form setjast í stein ("to sit in a stone") or ganga í stein ("join a stone"), whereas the word stone referred to a monastery. Literally meaning "to sit in a holy stone", from setjast ("to sit") + í ("in") + helgan, accusative masculine of helgur ("sacred, holy") + stein, the accusative singular of steinn ("stone").

setjast í helgan stein

1. (idiomatic) to retire, to go into retirement

• Icelandic Web of Science: Ég er sagður sestur í helgan stein. Hvar finn ég „helga steininn“!? (“They say I've sat in a holy stone, where can I find this holy stone!?”)
• Directorate of Health — Information about the idiom