This is a very commonly used English expression which has its roots in the nautical world although it is now used in a much less literal way. If you would like to find out when to use it then keep reading this article!
The expression is used to denote the act of making a big effort. Most commonly it refers to the spending of money and the act of spending more than usual in order to mark a special occasion.
The first recorded example of the phrase dates to the year 1937 in J. Curtis’ You’re in Racket. The phrase reads “this bloke you’re meeting up the Old Jacket and Vest to-night, let him push the boat out. Surely he can pester for a tightener if you’re hungry.” At this time the phrase was used to denote the act of buying someone a round of drinks.
It is unclear when the meaning of the expression was extended but it is suggested that this happened gradually sometime over the latter half of the 20th century.
An example of the phrase in use can be found in a quote made by English actor, Stephen Fry. It reads “I have pushed the boat out as far as I should in terms of taking on too many things. I’m getting older and I just could not take it any more. I am now monitoring myself very closely and I’m just trying not to get into that sort of state again.”