https://bosworthtoller.com/49666

Gesidian, a verb, “to put in order, to arrange”
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https://bosworthtoller.com/12988

Fyrn, adv. “ of old, formerly”
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Fyrnsidere, an unattested neologism, An agent noun derived from gesidian, meaning “old arranger” or maybe “former coordinator” Or if you are creative, “ex-coach”…

But one thing it does not mean is “ Follower of an ancient religion”.

Just saying.