en_tn/2sa/03/06.md

It came about

This introduces a new event in the story of the struggle between David's supporters and Saul's family. (See: rc://en/ta/man/translate/writing-newevent)

house of Saul

This refers to Saul's family and supporters who assumed control of his estate after he died.

house of David

This refers to the supporters of David.

Abner made himself strong in the house of Saul

Abner's increasing power over Saul's family is spoken of as if he became physically stronger. AT: "Abner gained more power over the family and supporters of Saul" (See: rc://en/ta/man/translate/figs-metaphor)