Where does “undercrypt” come from?

undercrypt (English) comes from English under, from Middle English under, from Old English under, from Proto-Germanic under, from Proto-Indo-European h₁entér, from Proto-Indo-European h₁en — in; in, inside.

undercrypt (English): A lower crypt or vault

Definitions

A lower crypt or vault

Ancestry of “undercrypt”, step by step

undercrypt traces back through two separate lines of ancestry.

via English under

Step	Language	Word	Meaning
1	English	under	In or at a lower level than; As a subject of;...
2	Middle English	under	under
3	Old English	under	under, beneath
4	Proto-Germanic	under	among, between; under, beneath; under
5	Proto-Indo-European	h₁entér	between
6	Proto-Indo-European	h₁en	in; in, inside

via English crypt

Step	Language	Word	Meaning
1	English	crypt	A cave or cavern; An underground vault,...
2	Latin	crypta	underground passage, tunnel; crypt; underground...
3	Ancient Greek	κρυπτός	concealed, hidden, secret
4	Ancient Greek	κρύπτω	to hide, cover; to conceal, obscure
5	Proto-Indo-European	krāu-	—

Every word from Proto-Indo-European h₁en →Every word from Proto-Indo-European h₁entér →Every word from Proto-Germanic under →