Another interpretation: [he was called Putiel] because at first he fattened [pittem] calves for idols. Kenite [from kanah, "acquired"], because he acquired Heaven for himself and acquired Torah for himself.
Jethro Who Once Fattened Calves for Idols and Then Acquired Torah
Yalkut Shimoni on Nach 38:2
דבר אחר שמתחלה פטם עגלים לאלילים. קיני שקנה לשמים וקנה לו תורה.