Par monts et par vaux

Annette a couru par monts et par vaux pour trouver une boulangerie ouverte un lundi à 13h. Spoiler : elle a fini au supermarché.
The French expression par monts et par vaux means “over hills and through valleys,” or, more broadly, “all over the place.”  It evokes someone trekking across every possible landscape, both literal and metaphorical, like a determined pilgrim in search of carbs. Unlike the English “over hell and breakfast,” however, it doesn’t imply chaos, exasperation, or cosmic mismanagement. The latter is also more colloquial and rough in tone.

Monts means mountains or hills.  Vaux is the plural of val - an archaic word for valley.  So the phrase literally means: through mountains and valleys.  The word vaux survives almost exclusively in fixed expressions like this one, or in toponyms, like château de Vaux-le-Vicomte.

Origin

The phrase dates back to the Middle Ages, when poets and knights loved to describe long journeys using grand imagery from nature. Travel back then meant trudging through hills, valleys, mud, questionable bridges, and the occasional disgruntled goose, in search of markets, work, or gossip. Over time, the expression shifted from a literal description of rugged travel to a figurative way of saying “everywhere” or “far and wide.”

Today, it adds a slightly old-fashioned, almost literary charm to any tale of relentless wandering. The pairing of opposites (mountains and valleys) is also a classic rhetorical device called merism, where two extremes are invoked to suggest the whole.

Examples

Depuis qu’ils ont pris leur retraite, ils courent par monts et par vaux pour voir leurs petits-enfants.
Since they retired, They've been dashing all over the place to visit their grandchildren.

Les journalistes ont couru par monts et par vaux pour couvrir l’événement.
The journalists raced far and wide to cover the event.