busman's holiday

From Wiktionary

[edit] English

[edit] Etymology

Reputedly, in the days of horse drawn vehicles the busmen would become fond of their horses and would ride the buses on their days off to assure the animals were being treated well by the substitute drivers.

[edit] Noun

busman's holiday (plural busman's holidays)

1. (idiomatic) A holiday or vacation during which you do the same thing that you do for your usual work