Noble titles are a poor comparison since they're the rare example where there actually is an exclusively-male root form. For most words the root form is neuter, and both male-only (if it exists) and female-only forms require an affix.
Properly, a male lich is "werlich" and a female lich is "wiflich" (unlike other words the /f/ sound is not likely to disappear); the plurals add "-en". But generally sex is irrelevant for undead{cn} so the neuter form by far predominates.
"lichess" is an abominable mixture of German and French roots ... so naturally it is indistinguishable from the rest of English.
note - "chess" is not a Germanic word (deriving from the Arabic شَاه (shah), meaning king). Ironically enough, it comes to English via the Old French eschés, meaning that "lichess" is arguably made from entirely French roots.
Hm, I guess the "libre" is French, but "live", "light", and most importantly "lich" are all German.
If we look for relatives of "libre", they include "leed"(song) and the first half of Leopold (adding "bold") and Luther (adding "army"). The common meaning is "people".
