Pattern
Middle English patron ‘something serving as a model’, from Old French (see patron). The change in sense is from the idea of a patron giving an example to be copied. Metathesis in the second syllable occurred in the 16th century. By 1700 patron ceased to be used of things, and the two forms became differentiated in sense.
wiktionary
From earlier patten, paterne, from Middle English patron(“patron; example”), from Old French patron, from Medieval Latin patrōnus(“patron”). Doublet of patron.
etymonline
pattern (n.)
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.
pattern (v.)
1580s, "to make a pattern for, design, plan" (a sense now obsolete), from pattern (n.). Meaning "to make something after a pattern" is from c. 1600; that of "to cover with a design or pattern" is by 1857. To pattern after "take as a model" is by 1878.
