Definition of "unwearing"

There is an unfailing charm about his novels, an unwearing freshness.

1894, Harper's New Monthly Magazine, volume 89, number 534, page 787

[…] he little knew what strength, a great, moral effort, a stern, unbending will, and an unwearing faith, will impart, even to one so young as that heroic girl, […]

1851, Snow Drop: Juvenile Magazine, volume 1, page 294