I'm trying to come up with a term that can roughly be taken to mean a period of fifty years. This term has to be based on ancient Greek, but it doesn't have to be an exact translation. The term can be twisted about and bastardized a little, as long as the root meaning could be worked out.

I've come up with a couple possibilities working on my own and using Google, but ancient Greek translations are not straightforward things on the Internet, and I know very little compared to some of the knowledgeable people here.

So far I have Pentechron and Pentekost as options. For example, a person living in the year 159 could say that they were living in the ninth year of the Fourth Pentechron (the fourth period of 50 years). Would one or either of these terms work, given what I've outlined above?

Are there any other suggestions you might make as to cool-sounding terms that could be derived from whatever the actual translation is?