Meaning

noun making or becoming suitable; adjusting to circumstances

noun a small and often standardized accessory to a larger system

noun (usually plural) furnishings and equipment (especially for a ship or hotel)

originFrom fit (“to conform to in shape or size; to be suitable for”, verb) + -ing (suffix forming present participles of verbs, and gerunds and nouns denoting the act of doing something or the embodiment of an action).

Etymology from Wiktionary, CC BY-SA 3.0