off and on

1. Also, on and off.

2. Intermittently, from time to time. For example, I read his column off and on , or We've been working on the garden all summer, on and off . [Early 1500s]

3. Also, off again, on again ; on again, off again . Uncertain, vacillating, as in Theirs is an off again, on again relationship , or The peace talks are on again, off again . Some believe this term originally referred to minor railroad accidents, where a train went off track and then on again. [Mid-1800s]