Wikipedia sagt:
English: 1463, from break (v.) + fast (n.). Cf. Fr. déjeuner "to breakfast," from L. dis-jejunare "to break the fast." The verb is from 1679.
The English name derives from the concept that one has not eaten while sleeping, i.e., one is fasting during that time, and one breaks that fast with the meal. The meaning is therefore the same as the French déjeuner or petit déjeuner and the Spanish desayuno. The German Frühstück, the Danish morgenmad, the Esperanto matenmanĝo, the Japanese asagohan or asameshi (朝飯), the Chinese zao can (早餐), and the Hebrew aruchat boker (ארוחת בוקר) mean "morning meal."
The Portuguese pequeno almoço, meaning "little lunch", like its eastern neighbors, France and Spain. In Brazil, breakfast is café da manhã, the "coffee of the morning".
Ich frage mich, ob es vor der Chritianisierung der Engländer eine andere Bezeichnung für das Frühstück gab.