Why where the children of Israel called Hebrews?

The Word Hebrew comes from the Hebrew Word Ivri (עברי). It's theorized that this Word is related to the Hebrew Word ever (עבר) which means "beyond". It's a reference to Abraham coming from "beyond the river".

Answer:
The name "Hebrews" comes from Ever (see Genesis ch.10), and refers to all of Ever's descendants, one of whom was Abraham (Genesis ch.11).
However, once we received the name of Israel (Genesis ch.35), we preferred to use that name instead of "Hebrews," because "Hebrews" is generic, while Israel is a title of honor.