For those (two) of you holding your breath to hear the source of "tootle with vigor," here you go:
- More than 300 million people in the world speak English and the rest, it sometimes seems, try to. It would be charitable to say that the results are sometimes mixed. Consider this ... warning to motorists in Tokyo: "When a passenger of the foot heave in sight, tootle the horn. Trumpet at him melodiously at first, but if he still obstacles your passage, then tootle him with vigor."
. . . .
[I]t would appear that one of the beauties of the English language is that with even the most tenuous grasp you can speak volumes if you show enough enthusiasm--a willingness to tootle with vigor, as it were.
-Bill Bryson in The Mother Tongue: English & How It Got that Way