mid-14c., from whole (adj.) + -ness. Old English had halnes.
Entries linking to wholeness
whole adj.
Old English hal "entire, whole; unhurt, uninjured, safe; healthy, sound; genuine, straightforward," from Proto-Germanic *haila- "undamaged" (source also of Old Saxon hel, Old Norse heill, Old Frisian hal, Middle Dutch hiel, Dutch heel, Old High German, German heil "salvation, welfare"), from PIE *kailo- "whole, uninjured, of good omen" (source also of Old Church Slavonic celu "whole, complete;" see health).
The spelling with wh- developed early 15c. The sense in whole number is from early 14c. Whole milk is from 1782. On the whole "considering all facts or circumstances" is from 1690s. For phrase whole hog, see hog (n.).
-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).