y-sh-ʿ — to save, to deliver, to rescue
י.ש.ע (yasha) is the salvation root — behind yeshuah, hoshana, and the names Joshua, Isaiah, Hosea and Yeshua.
The word family
Every word below is built on י.ש.ע. Same three letters, different vowels and prefixes.
Two words fused: the imperative הוֹשַׁע plus נָא, "please". The origin of "hosanna".
Shortened over time to יֵשׁוּעַ (Yeshua), the form common in the Second Temple period.
What I tell students about this root
Almost every form you meet is Hif'il, the causative binyan — the root does not really do "to be saved" on its own, it does "to cause rescue". And because the first letter is yod, it disappears in the Hif'il and you get a vav sound instead: hoshia, moshia, yeshuah. Recognising that swap is what lets you spot the root inside a name.