Old English inweard "inmost; sincere; internal, intrinsic; deep," from Proto-Germanic *inwarth "inward" (source also of Old Norse innanverðr, Old High German inwart, Middle Dutch inwaert), from root of Old English inne "in" (see in (adv.)) + -weard (see -ward). As an adverb, Old English inneweard. As a noun in late Old English, "entrails, intestines."
-ness
word-forming element denoting action, quality, or state, attached to an adjective or past participle to form an abstract noun, from Old English -nes(s), from Proto-Germanic *in-assu- (cognates: Old Saxon -nissi, Middle Dutch -nisse, Dutch -nis, Old High German -nissa, German -nis, Gothic -inassus), from *-in-, originally belonging to the noun stem, + *-assu-, abstract noun suffix, probably from the same root as Latin -tudo (see -tude).