Sabesdiker losn
Der sabesdiker-losn (Yiddish: דער סאַבעסדיקער לשון (לאָסן)) is a dialectal feature characteristic of the Northeastern dialect of the Yiddish language (NEY, Litvisher-vaysrusisher dialekt, צפֿון ייִדיש Tsofn-yidish), which is the replacement, or merger of the "hushing" (post-alveolar) consonants "ch", "sh" (IPA: /tʃ/, /ʃ/), with the "hissing" (alveolar) ones, "ts", "s" (IPA: /ts/, /s/). The name of the term is a shibboleth: the phrase "דאָס שבתֿדיקע לשון" dos shabesdike loshn (in standard Yiddish) means 'Sabbath speech', hinting at the perception that this feature is substandard.