In other words, Friedelein. OK! But that doesn't help Swiff, who just wants to know how many German-speaking medieval Irish namers there were ... or the extent to which people felt free to use "foreign" names, if they knew them.
Is there a regional difference between -lein and -chen as diminutive indicators? (You'll know, if anyone does!)
Gretel versus
Gretchen? If so, that might narrow it down slightly.