Toot :Slang, has several meanings,in this case maybe :
the noise made by a horn,whistle.
I´ve found this :
One more safety item: pull the turn signal lever and a horn gives two quick "toots" to warn pedestrians the car is around.
I´ve also found " 2 Toots Train Whistle Grill "....je ,je... Quite onomatopoeic !
I agree with Melati that the sence sense is of something fast,quick .
Hope this helps you!
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