Euros

Source: High School Fleet

Author: Me

Year: 2016

These subtitles are actually kinda wack in retrospect.
They're not laughing about her mentioning the currency Euros, they're laughing at her choice of pronoun when adressing herself (Washi 儂 instead of Watashi 私).

"Washi" is not commonly used in modern Japan.
It's often used in Anime to depict a character as being old, or from a different era, or maybe just being generally eccentric.