"state of being solitary or alone," 1590s, from lone (adj.) + -ness.
Entries linking to loneness
lone adj.
late 14c., "having no companion, solitary, apart from any other," shortening of alone (q.v.) by weakening of stress or else by misdivision of what is properly all one. Used attributively, while the full form is used in the predicate. Compare live (adj.), from alive; colloquial 'long for along. The Lone Star in reference to Texas is first recorded 1843, from its flag when it was a nation. Lone wolf in the figurative sense is 1901, American English.
-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).