# crippled in his feet

This phrase means "unable to walk."

# five years old

This was the age of Jonathan's son at the time of his father's death. 

# the news about Saul and Jonathan

This refers to the news about their death.

# nurse

This is a woman or girl who is hired to care for young children.

# became lame

This explains how Mephibosheth was injured so he was unable to walk.

# Mephibosheth

This is the name of Jonathan's young son, the grandson of Saul.