A book about the Camino entitled The Way is Made by Walking, by Arthur Paul Boers, led us to look for the origin of this phrase. It comes in fact from a well known poem by the Spanish poet Antonio Machado, who died in 1939. Here it is:
Caminante, son tus huellas
el camino, y nada más;
caminante, no hay camino,
se hace camino al andar.
Al andar se hace camino,
y al volver la vista atrás
se ve la senda que nunca
se ha de volver a pisar.
Caminante, no hay camino,
sino estelas en la mar.
And in English:
Wanderer, your footsteps are
the path, and nothing else;
wanderer, there is no path,
the path is made by walking.
Walking makes the path,
and on glancing back
one sees the path
that will never trod again.
Wanderer, there is no path—
Just waves in the sea.
Personally my preferred book concerning the Camino is by a Jesuit priest Kevin A Codd and is entitled: To the Field of Stars. The author points out that Compostella is possibly derived from the Latin: campo, meaning a field and stella meaning a star. Another possibility, however, is that it comes from compostum, meaning a cemetary!