Here is a favorite Russian tune, in a great setting —
Katyusha is a tender diminutive from the female name Ekaterina (Catherine): Katya is the nickname and Katyusha, a tender diminutive.
This is a Russian Soviet wartime song about a girl longing for her beloved, who is away on military service. The music was composed in 1938 by Matvei Blanter and the lyrics were written by Mikhail Isakovsky. It was first performed by the celebrated Russian folk singer, Lidiya Ruslanova.
And here is Ruslanova singing the song for Russian troops: