The origin of "splurge" is somewhat obscure but is believed to be an expressive, onomatopoeic coinage from the 19th century, possibly meant to suggest the sound or feeling of something bursting or spreading out extravagantly. It first appeared in American English with the sense 'to make an ostentatious display', which naturally evolved to its primary modern meaning related to extravagant spending. The word's playful and slightly explosive phonetic quality effectively conveys the sense of sudden, unrestrained excess it describes.

The word "splurge" is considered a simplex word. It is an expressive formation, likely imitative or of unknown origin, and does not break down into meaningful, established morphemes within the English spelling.