E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Nurse an Omnibus (To)
is to try and run it off the road. This is done by sending a rival omnibus close at its heels, or, if necessary, one before and one behind it, to pick up the passengers. As a nurse follows a child about regardless of its caprices, so these four-wheel nurses follow their rival.