This is the word for chair (jatēna*) with an augmentative suffix, making it the word for ‘throne’ or some other sort of elevated or important seat. One could refer to the chair at the head of the table as jatēnar, or a judge’s bench, etc. And of course, Sauron’s favorite hangout:
se jān mo mārōn maxē sū jatēnar jaxē;
One for the dark lord on his dark throne
*I haven’t blogged these words yet.