patron n.

Old English fæder "he who begets a child, nearest male ancestor;" also "any lineal male ancestor; the Supreme Being," and by late Old English, "one who exercises parental care over another," from Proto-Germanic *fader (source also of Old Saxon fadar, Old Frisian feder, Dutch vader, Old Norse faðir, Old High German fatar, German vater; in Gothic usually expressed by atta), from PIE *pəter- "father" (source also of Sanskrit pitar-, Greek pater, Latin pater, Old Persian pita, Old Irish athir "father"), presumably from baby-speak sound "pa." The ending formerly was regarded as an agent-noun affix.

My heart leaps up when I behold

  A rainbow in the sky:

So was it when my life began;

So is it now I am a man;

So be it when I shall grow old,

  Or let me die!

The Child is father of the Man;

I could wish my days to be

Bound each to each by natural piety.

[Wordsworth, 1802]

The classic example of Grimm's Law, where PIE "p-" becomes Germanic "f-." Spelling with -th- (15c.) reflects widespread phonetic shift in Middle English that turned -der to -ther in many words, perhaps reinforced in this case by Old Norse forms; spelling caught up to pronunciation in 1500s (compare mother (n.), weather (n.), hither, gather). As a title of various Church dignitaries from c. 1300; meaning "creator, inventor, author" is from mid-14c.; that of "anything that gives rise to something else" is from late 14c. As a respectful title for an older man, recorded from 1550s. Father-figure is from 1954. Fathers "leading men, elders" is from 1580s.

a Modern English variant of patron, retaining its other old sense of "outline, plan, model, an original proposed for imitation," from Old French patron "patron, protector; model, pattern." The difference in form and sense between English patron and pattern wasn't firm before 1700s. The meaning "a design or figure corresponding in outline to an object that is to be fabricated and serving as a guide for its shape and dimensions" is by late 14c. Extended sense of "repeated decorative design" is from 1580s. From 1640s as "a part showing the figure or quality of the whole." Meaning "model or design in dressmaking" (especially one of paper) is recorded by 1792 (Jane Austen). Pattern-book is from 1774; pattern-maker is by 1851; pattern baldness is by 1916.