The word 'thoughtlessness' is a layered construction built entirely from native Germanic elements. Its foundation is 'thought', which originates from the Old English verb for thinking, 'þencan'. The suffix '-less', meaning "without," was attached to create the adjective 'thoughtless', describing someone devoid of consideration or care. Finally, the abstract noun-forming suffix '-ness' was added to transform the adjective into a noun denoting the permanent state or quality of being inconsiderate or heedless. This tripartite structure elegantly and transparently encodes the concept from the core idea ('thought'), through the negation of that quality ('-less'), to the final abstraction of that negated state ('-ness').

Structure: thought (mind, consideration) + less (without) + ness (state or quality) - thought: From Old English 'þōht', 'geþōht', meaning "process of thinking, a thought." Germanic origin, related to the verb 'think'. Functions as the core noun root. - less: From Old English '-lēas', meaning "free from, without." A Germanic adjectival suffix used to form adjectives indicating absence. - ness: From Old English '-nes(s)', a noun-forming suffix denoting a state, quality, or condition. Germanic origin.