What word does your mother always say?
late 14c. (twilighting), a compound of twi- + light (n.) Cognate with Dutch tweelicht (16c.), German zwielicht. Exact connotation of twi- in this word is unclear, but it appears to refer to "half" light, rather than the fact that twilight occurs twice a day. Cf. also Sanskrit samdhya "twilight," literally "a holding together, junction," Middle High German zwischerliecht, literally "tweenlight." Originally and most commonly in English with reference to evening twilight but occasionally used of morning twilight (a sense first attested mid-15c.). Figurative extension is first recorded c.1600.