ZWIEBACK
zwieback, rusk, Brussels biscuit, twice-baked bread
(noun) slice of sweet raised bread baked again until it is brown and hard and crisp
Source: WordNet® 3.1
Etymology
Noun
zwieback (countable and uncountable, plural zwiebacks)
a usually sweetened bread enriched with eggs that is baked and then sliced and toasted until dry and crisp
a teething food for toddler children
Source: Wiktionary
Zwie"back`, n. [G., fr. zwie-two, twice (see Twice) + backen to
bake.]
Definition: A kind of biscuit or rusk first baked in a loaf and afterwards
cut and toasted.
Source: Webster’s Unabridged Dictionary 1913 Edition