This is an imitation of the speech of either a small child or a person who suffers from rhotacism (also known, confusingly, as de-rhotacism). This condition is the inability to articulate an 'r' sound. Very young children often struggle to pronounce 'r' sounds, and a proportion of adults remain unable to do this. The attempt to pronounce an 'r' usually comes out as something like a 'w' sound. If the speaker is a small child, writing their attempts to say 'trip on a train' as 'twip on a twain' makes them sound cute; if the speaker is an older child or an adult with a speech impediment, the writer is mocking them.

Hello Kai, this is a spelling error and is meant to say ‘take a trip on a train’ Hope this helps!

Great song from Frank Sinatra: https://www.youtube.com/watch?v=FPsgdRlv0CM

thank you very much Chris

This mocks a person who pronounces R as W. “trip on a train”