1590s, "imprudence," from inconsiderate + -ness. From 1858 as "want of consideration for others."
Entries linking to inconsiderateness
inconsiderate adj.
late 15c., "done thoughtlessly, heedless, careless, indiscreet," from Latin inconsideratus "headstrong, unadvised," of persons, "thoughtless," literally "not properly considered," from in- "not, opposite of" (see in- (1)) + consideratus (see consider). Sense of "without regard for the feelings of others" is from 1842. Related: Inconsiderately.
-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).