Origins
The word 'loaf' is one of the most ancient and consequential in the English language — not because of what it names, but because of what it built. From this humble word for bread, the English language derived its words for the two highest ranks of the household: lord and lady. The history of 'loaf' is the history of bread as the foundation of social order.
The word descends from Old English 'hlāf' (bread, loaf), from Proto-Germanic *hlaibaz (bread, loaf). The Proto-Germanic word appears across the Germanic languages: German 'Laib' (loaf), Swedish 'lev' (archaic for loaf), Gothic 'hlaifs' (bread). The ultimate origin of *hlaibaz is debated. Some scholars propose a connection to Proto-Slavic *xlěbъ (bread), visible in Russian 'хлеб' (khleb), Polish 'chleb,' and Czech 'chléb.' Whether Germanic borrowed from Slavic, Slavic from Germanic, or both from an unknown third source (perhaps connected to early agriculture) remains unresolved.
The social derivatives of 'hlāf' are extraordinary. Old English 'hlāfweard' — literally 'loaf-guardian,' from 'hlāf' (bread) + 'weard' (guardian, ward) — became 'lord' through centuries of phonetic erosion. The lord of the household was the guardian of its bread supply. The word 'hlaford' (an intermediate form) contracted to 'lord' by the thirteenth century. Similarly, Old English 'hlǣfdige' — literally 'loaf-kneader,' from 'hlāf' (bread) + a word related to 'dǣge' (kneader, from the root of 'dough') — became 'lady.' The lady of the household was the one who made the bread. The entire structure of the Anglo-Saxon household was expressed through bread: who made it, who guarded it, and who received it.
Old English Period
The feast day of Lammas (August 1st), one of the major dates in the Anglo-Saxon calendar, also derives from 'hlāf.' The name comes from Old English 'hlāfmæsse' — 'loaf-mass' — the day when the first loaf from the new harvest was brought to church and blessed. Lammas marked the beginning of the harvest season and was both a religious and economic milestone. The word survives in place names across England.
The verb 'to loaf' (to idle, to spend time doing nothing) is surprisingly unrelated to the noun. It appeared in American English in the 1830s and may be a back-formation from 'loafer,' which itself is of uncertain origin — possibly from German 'Landläufer' (vagabond, literally land-runner) or from 'lōfer,' a dialectal form. The coincidence of spelling has led to many folk etymologies, but the bread-word and the idling-word have separate histories.
The plural of 'loaf' — 'loaves' — preserves the Old English pattern where final voiceless fricatives (the 'f' sound) became voiced (the 'v' sound) before a vowel. The same pattern explains 'knife/knives,' 'wife/wives,' 'life/lives,' 'half/halves,' and 'wolf/wolves.' This alternation is one of the oldest surviving grammatical features of English, predating the Norman Conquest.
Legacy
Bread itself was the staple of the medieval English diet, accounting for the majority of calories consumed by common people. The centrality of bread to survival explains why the word for bread could generate the words for the most important people in the household. In a world where the grain harvest determined whether a community would live or starve through winter, the guardian of the bread was, quite literally, the guardian of life.