Note the very simple easy trick: I search for "Jehan BYNAMEIWANTODOCUMENT", in quotes, in googlebooks. A very easy way to get medieval hits for French bynames.
Culturally Mixed Names: Names that mix name phrases from different times and/or places are allowed if the name meets one of the following conditions.
a. The name mixes name phrases found in a single regional naming group as listed in Appendix C that are dated to within 500 years of one another.
b. The name mixes name phrases from two regional naming groups that are listed in Appendix C as combinable and those name phrases are dated to within 300 years of one another.
Names that combine more than two regional naming groups or that combine two regional naming groups that are not listed as combinable will not be allowed under this rule (though they may be registered under the allowances in sections c and d below).
c. The name mixes name phrases from naming pools that can be documented as having been used together in the personal names of real people; for such combinations, the name phrases must be within 300 years of one another (and within 300 years of the documented examples). For such documentation, at least three period examples must be included in which the names can only be understood as combining from separate naming pools. The borrowing of names from one naming pool into another is not sufficient to demonstrate this, nor is the translation of names into another language.
d. A name which includes name phrases documented under the legal name allowance, the grandfather clause, or the branch name allowance follows special rules. These name phrases are treated as neutral in language and time. Such name phrases may be combined with name phrases from a single regional naming group dated to within 500 years of one another. They may not be combined with name phrases from two or more regional naming groups. If a name phrase can also be documented as either an attested or constructed name, it may be treated in whichever way is more favorable for registration.
In addition, if a grandfathered name phrase was found in a registered name that combined languages from two or more regional naming groups, the new submission may combine those same regional naming groups. If this allowance is used, then no new regional naming group may be added.
Naming resource links archive of Academy of S. Gabriel, which is not SCA but does have very high standards
These are lists of how names may have persisted over time
"IGI Batch Numbers - British Isles and North America"
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