borrowed from New Latin, from Greek aden-, adḗn
"gland" (of uncertain origin) + New Latin -o- -o-
Greek adḗn "gland" is traditionally compared with Old Norse økkr "lump, tumor, swelling" (going back to *engʷo-) and Latin inguen "swelling on the groin, groin." However, adḗn, if it reflects Indo-European *n̥gw-ēn, would seem to come from a vowel-initial root *engw-, which violates a generally accepted constraint on vowel-initial roots in Indo-European; on the other hand, if the root were laryngeal-initial, the form *h1ngw- should have yielded *end- in Greek, this allegedly being the regular outcome of the sequence laryngeal/resonant/stop. Hence adḗn may be without Indo-European congeners.