וַֽיַּחְפְּרוּ֙ בְּאֵ֣ר אַחֶ֔רֶת וַיָּרִ֖יבוּ גַּם־עָלֶ֑יהָ וַיִּקְרָ֥א שְׁמָ֖הּ שִׂטְנָֽה׃
And they digged another well, and they strove for that also. And he called the name of it Sitnah.
Radak on Genesis
ויחפרו...שטנה, from the word “Satan.” The name reflected the fact that every time they dug with success they would be subjected to this hatred.
Daat Zkenim on Genesis
ויקרא שמה שטנה, “he called its name Sitnah. (hatred, enmity) He had given the Philistines the benefit of the doubt regarding denying his claim to the first well his servants had dug. But now he knew that that had not been mere coincidence, but a display of their hatred of him.