Ahsoka's nickname, 'Snips' was given to her during the battle of Christophsis by Anakin Skywalker, her master. It started with Skywalker being so stubborn about accepting her as a Padawan, and calling her a youngling even though she was 14 and Anakin was only 9 when he became a Padawan.

Why did Anakin call ahsoka snips?

Yoda assigns her to Anakin to teach him a greater sense of responsibility, and Anakin is initially frustrated by this decision. Their early interactions are "playfully contentious", with Anakin calling her "Snips" for her "snippy" attitude and Ahsoka calling him "Skyguy" as a pun on his surname.

When did Anakin last call ahsoka snips?

SPOILERS - I though, and still in my mind it is, that when on rebels season 2 finale anakin says her name, the "good" version says "snips". Its a lot more emotional.