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1828, "ostentatious display," American English, a Western (i.e. Kentucky) word, perhaps a blend of splash and surge. The meaning "extravagant indulgence in spending" is first recorded 1928.
"to make an ostentatious display, to put on a splurge" (in the older sense of the noun), by 1848, from splurge (n.). Thornton's "American Glossary" has an 1848 citation defining splurge (v.) as "to expatiate at large, to appeal to broad and general principles." Meaning "to spend extravagantly" is by 1934. Related: Splurged; splurging.