pattern [ME] Originally pattern and patron were the same word. Patron comes, via French, from Latin patronus ‘protector of clients, defender’, a sense which explains J. K. Rowling’s use of ‘Patronus’ for a spell that produces a protecting animal in the Harry Potter books. The word goes back to pater ‘father’ (see further at pope). The word pattern developed from the idea of a patron giving an example to be copied. The swapping round of sounds (metathesis) of the vowel and the ‘r’ occurred in the 16th century, and by 1700 patron ceased to be used of things, and the two forms developed different senses.