Why are temporary lodging places called 'digs'?

It’s short for diggings, which is the older word for the same idea. That derives — as you might guess — from a place where one digs, a word that goes back to the sixteenth century. Many books argue that the original diggings linked to the accommodation sense were the gold fields of California and Australia. We do know that the Australian nickname digger comes from this area of life and so it’s sometimes assumed that the word is likewise Australian, though all the early evidence is American and the term predates both these gold rushes anyway. But there is a gold fields connection.