Den
Den (den) , noun
[Anglo-Saxon denn; perh. akin to German tenne floor, thrashing floor, and to Anglo-Saxon denu valley.]
1.
A small cavern or hollow place in the side of a hill, or among rocks; esp., a cave used by a wild beast for shelter or concealment; as, a lion's den; a den of robbers.
2.
A squalid place of resort; a wretched dwelling place; a haunt; as, a den of vice.
Those squalid dens, which are the reproach of great capitals.
3.
Any snug or close retreat where one goes to be alone. [Colloquial]
4.
A narrow glen; a ravine; a dell. [Old English & Scotch] — Shakespeare
Den , intransitive verb
To live in, or as in, a den.
The sluggish salvages that den below.