Meaning

adjective acting or moving or capable of acting or moving quickly

adverb quickly or rapidly (often used as a combining form)

noun abstaining from food

originFrom Middle English fasten, from Old English fæstan (“to fast”), from Proto-West Germanic *fastēn, from Proto-Germanic *fastāną (“to fast”), from the same root as Proto-Germanic *fastijaną (“to fasten”), derived from *fastuz, and thereby related to Etymology 1. The religious sense is presumably introduced in the Gothic church, from Gothic 𐍆𐌰𐍃𐍄𐌰𐌽 (fastan, “hold fast (viz. to the rule of…

Etymology from Wiktionary, CC BY-SA 3.0