Reference for Chullin 2:8

הַשּׁוֹחֵט לְשֵׁם הָרִים, לְשֵׁם גְּבָעוֹת, לְשֵׁם יַמִּים, לְשֵׁם נְהָרוֹת, לְשֵׁם מִדְבָּרוֹת, שְׁחִיטָתוֹ פְסוּלָה. שְׁנַיִם אוֹחֲזִין בְּסַכִּין וְשׁוֹחֲטִין, אֶחָד לְשֵׁם אַחַד מִכָּל אֵלּוּ, וְאֶחָד לְשֵׁם דָּבָר כָּשֵׁר, שְׁחִיטָתוֹ פְסוּלָה:

When a person slaughtered an animal in or to the name of mountains, hills, seas, rivers, or deserts, it is Pasool. When one of two persons holding the same knife had killed the animal with the mentioned idolatrous intention, and the other with a lawful intention, the animal so killed is Pasool.

Jastrow