Line up onion means stand on a single line. but the expression did not always have the same meaning. At the beginning of the 17th century, this expression meant "to take place somewhere where one is not invited".
It was long believed that this was an allusion to the way the peasants had to tie onions together with straw: from the largest to the smallest. However, one should not read "row of onions", like the vegetables, but "row of Onion", like the master of ceremonies Artus de la Fontaine Solaro, baron of Onion. He was in charge of assigning places to deputies under Henry II and made himself known thanks to the severity with which he made them close ranks and respect the given places.
- Treasures of French expressions by Sylvie Weil. Belin, 2008.
- La Fin des haricots: And other mysteries of French expressions by Colette Guillemard. Omnia, 2009.