from The American Heritage® Dictionary of the English Language, 4th Edition
- Yesterday: yesternight.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- Belonging to the day preceding the present; next before the present.
- Denoting former, earlier, or previous times.
Middle English, from Old English geostran.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Middle English yester-, yister-, from Old English ġeostran-, ġiestran- ("previous day, prior day"), from Proto-Germanic *gistr- (“yesterday”), from Proto-Indo-European *dʰǵʰyes- (“yesterday”). Cognate with Gothic 𐌲𐌹𐍃𐍄𐍂𐌰- (gistra-, "tomorrow"), Ancient Greek χθές (khthés, "yesterday"). More at yesterday. (Wiktionary)