What speakers mean by it now
In ordinary English, father names a male parent: the man who begets a child, who adopts one, or who raises one. The same word also covers a male ancestor further back, a priest addressed by title, God in Christian usage, a founder of a craft or nation, and, in the plural, the elders of a town. Those extra jobs sit on top of the kinship sense. They did not replace it.
The origin of the word father is inheritance, not borrowing. Latin pater is a cousin, not a source. English already had the native form when it first appears in writing.
A Germanic word from the beginning
Old English wrote fæder. The earliest records sit in the Old English period, before 1150; dictionaries that round early medieval dates often say before the twelfth century. The spoken word is older than any surviving manuscript. It came in with the language, from Proto-West Germanic into Old English, not from French after the Conquest and not from Latin in the schoolroom.
The Old English noun already carried more than one load. It meant the man who begets a child and the nearest male ancestor. It also meant a male ancestor in a longer line, and it named God. By late Old English it could describe someone who gave parental care without being the biological sire. Middle English kept the word as fader, still with d in the middle. The modern th is a later spelling of a later sound.
Germanic relatives make the family obvious: Old Saxon fadar, Old Frisian feder, Dutch vader, Old Norse faðir, Old High German fater, German Vater. Gothic is the odd one out in daily speech. Speakers there more often used atta for the everyday parent, though an inherited fadar is recorded. The split is a reminder that even a basic kinship term can be swapped for a nursery word in one branch and kept in the others.
The older root and two sound laws
Behind the Germanic forms stands Proto-Germanic fadēr. That reconstruction goes back to Proto-Indo-European ph₂tḗr, the same item older handbooks write as pəter-. From that root come Sanskrit pitṛ, Greek patēr, Latin pater, Old Persian pita, and Old Irish athair. Irish lost the initial p, which is why athair does not look like father until the rest of the word is lined up.
The opening consonant is a stock example of Grimm's Law. Indo-European p became Germanic f. Latin kept pater; English ended with an f. The inner consonant is the more interesting half of the story. Grimm's Law would have turned t into a voiceless th-sound. Germanic instead shows d: Old English fæder, German Vater. That d is Verner's Law. The ancestral accent sat on the second syllable, so the expected th voiced and later became d. Brother kept th because its accent sat on the first syllable. The two English kinship words still display where stress used to fall in the parent language.
The second half of the form is usually read as an old kinship suffix, the same sort of ending seen in mother, brother, and daughter, attached to a nursery syllable of the pa type. That last step is a reconstruction. Handbooks present it as likely, not as a fact copied from a tablet. The suffixes on the other kinship words may not all share one origin, even if they rhyme in the daughter languages.
Romance doublets sit beside the native English word because Latin pater traveled another road: padre, pater, French père. They are relatives. They are not the source of English father.
When the middle consonant changed again
The spelling father is younger than the word. In the fifteenth century a Middle English phonetic shuffle turned -der into -ther in a cluster of common items. Mother, weather, gather, and hither show the same movement. The converse happened in other words, so burthen and murther later settled back to d. Old Norse faðir, with a voiced th already in the middle, may have reinforced the change in this particular noun. Pronunciation moved first. Spelling caught up in the 1500s.
The vowel of modern father is a separate irregularity. Many accents that still give rather a short vowel give father a long ah, and historical phonology has not produced a closed explanation. The consonant history is clearer than the vowel history.
How the meaning spread
The biological and genealogical senses, and the divine one, were already in Old English. Later English borrowed the word's weight for offices and metaphors without emptying the original sense.
As a title for church dignitaries it is recorded from about 1300. Creator, inventor, author appears in the mid-fourteenth century. Anything that gives rise to something else is late fourteenth. Respectful address to an older man is recorded from the 1550s. Fathers as leading men or civic elders dates from the 1580s. The verb, to father a child or an idea, is built on the noun and is recorded from about 1400.
None of these later uses required a new root. Speakers kept stretching the same inherited stem: from the man in the household, to God, to a priest, to a founder, to a cause.
What the German cousin still shows
Set German Vater next to English father and the first Germanic shift is still audible: the old p became f on the Germanic side, while Latin pater kept the stop. The English th in the middle is a second, later change written over a Verner d. That sequence — inheritance from Old English fæder, Grimm's f, Verner's d, then a Middle English th — is the whole path, with no French detour in between.