Why does it say "Mefivoshes ben Yehonason ben Sha'ul"? (We know that Yehonason is ben Sha'ul!)
Malbim: Until now he was hiding; he hid his name and his family's name. Now he publicized it.
Why is he called "Meriv Ba'al" in Divrei ha'Yamim I, 8:34?
Shabbos 56b: His real name was Mefivoshes. He is called Meriv Ba'al because he made a Merivah (quarrel) with his Master. (When David said that Tziva will split the field with him, Mefivoshes was upset with Hashem, who returned David).
Malbim: One of these names is what he called himself when he was hiding.
Malbim citing Chazal: His real name was Meriv Ba'al. 1 He is called Mefivoshes because he shamed David in Halachah.
Our text in Brachos 4a says that Mefivoshes's real name was Ish Boshes. It seems that Malbim's text there said Meriv Ba'al, like Shitah Mekubetzes and Maharsha, 4a. (PF).