splash out
phrasal verb

- to spend a lot of money on buying things, especially things that are pleasant to have but that you do not need

Cambridge Dictionary

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WORD ORIGIN

Splash out most likely derives from the phrase "to make a splash“, which means to do something that draws attention to oneself or to suddenly become successful or well known.

The verb splash means

- to spread or scatter fluids through the air (to splash one's hands in the water)

- to apply patches or spots of a contrasting colour (the dress was splashed with pink and blue floral patterns), or

- to noticeably display or publicise something (the affair was splashed all over the daily newspapers)

Splash, which is first recorded in 1715, is believed to be an alteration of the Middle English plashe, which meant a pool of water. Use of the word in the context of a dazzling display was first recorded in 1804 and the adjective splashy, meaning sensational, appeared in 1836.

(sources: Online Etymology Dictionary, The Barnhart Concise Dictionary of Etymology, The American Heritage Dictionary)

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SYNONYMS

fork out, blow, pay out, cough up, open the purse, splurge, dig deep, indulge oneself, pay an arm and a leg for something, pay through the nose for something

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SMUGGLE OWAD into a conversation, say something like:

“The company used to SPLASH OUT thousands of euros firework celebrations. I think those days are new over.