pattern: [14] Etymologically, pattern and patron are the same word. When it arrived in Old French as patron (from Latin patrōnus), it had roughly the range of senses of modern English patron, including that of ‘one who commissions work’. But it had also acquired one other. Someone who pays for work to be done often gives an example of what he wants for the workman to copy: and so patrōnus had developed the meaning ‘example, exemplar’.
This passed into English from Old French along with the other meanings of patron, and not until the 17th century did it begin to be differentiated by the spelling pattern. The sense ‘decorative design’ emerged in the 16th century. => patron[pattern etymology, pattern origin, 英语词源]