Technically the middle ages didn't begin until
after the Anglo-Saxon era, which was in the post-Imperial "Dark
Age". Since Ine's brother was Ingild, it's probable Ine was not his full name (we frequently have only the common abbreviated names of
Saxon kings, but full names of their siblings). While Ine's predecessor (not father) had a British name (Cædwalla), as did many of the earlier kings of Gewisse claimed as Ine's ancestors, In-, though rare, is recorded in Germanic names outside Britain. No satisfactory meaning can be attached to the element though, as prosaic
in is merely a rather vague preposition, with no indication that the sense "indoor space, room, chamber" was widespread or early enough. It's possible that like the
Al- in
Alfred (short for Athelfred), it's merely an abbreviation for a more common element such as Ind- or Ing(w)-. While there's no better explanation of Ind- (some early Greek versions suggest
Hund- or
Gund- was the original in some cases, in others it may be Celtic or
Alan Vind — the Alans were an Iranian tribe from central
Asia pushed into the Empire with the Goths and Vandals), Ingwe/Ingui was an ancestral figure for some Germanic tribes and royal houses later raised to the status of a deity in the Norse pantheon.